Split ProxyResolverV8Tracing into an implementation and a wrapper.

net/proxy/proxy_resolver_v8_tracing_unittest.cc

Index: net/proxy/proxy_resolver_v8_tracing_unittest.cc
diff --git a/net/proxy/proxy_resolver_v8_tracing_unittest.cc b/net/proxy/proxy_resolver_v8_tracing_unittest.cc
index 296853c29bd9fcfca02f398ce50675640d256e7e..6eda3b854205b7bda20c2ded2dcbe99d233111e8 100644
--- a/net/proxy/proxy_resolver_v8_tracing_unittest.cc
+++ b/net/proxy/proxy_resolver_v8_tracing_unittest.cc
@@ -7,11 +7,8 @@
 #include <string>
 
 #include "base/files/file_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
-#include "base/stl_util.h"
-#include "base/strings/string_util.h"
-#include "base/strings/stringprintf.h"
+#include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
@@ -21,11 +18,7 @@
 #include "net/dns/host_cache.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/log/net_log.h"
-#include "net/log/test_net_log.h"
-#include "net/log/test_net_log_entry.h"
-#include "net/log/test_net_log_util.h"
 #include "net/proxy/proxy_info.h"
-#include "net/proxy/proxy_resolver_error_observer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
@@ -39,7 +32,7 @@ class ProxyResolverV8TracingTest : public testing::Test {
     // Drain any pending messages, which may be left over from cancellation.
     // This way they get reliably run as part of the current test, rather than
     // spilling into the next test's execution.
-    base::MessageLoop::current()->RunUntilIdle();
+    base::RunLoop().RunUntilIdle();
   }
 };
 
@@ -62,154 +55,153 @@ scoped_refptr<ProxyResolverScriptData> LoadScriptData(const char* filename) {
   return ProxyResolverScriptData::FromUTF8(file_contents);
 }
 
-scoped_ptr<ProxyResolverErrorObserver> ReturnErrorObserver(
-    scoped_ptr<ProxyResolverErrorObserver> error_observer) {
-  return error_observer;
-}
-
-scoped_ptr<ProxyResolver> CreateResolver(
-    NetLog* net_log,
-    HostResolver* host_resolver,
-    scoped_ptr<ProxyResolverErrorObserver> error_observer,
-    const char* filename) {
-  scoped_ptr<ProxyResolver> resolver;
-  ProxyResolverFactoryV8Tracing factory(
-      host_resolver, net_log, ProxyResolver::LoadStateChangedCallback(),
-      base::Bind(&ReturnErrorObserver, base::Passed(&error_observer)));
-  TestCompletionCallback callback;
-  scoped_ptr<ProxyResolverFactory::Request> request;
-  int rv = factory.CreateProxyResolver(LoadScriptData(filename), &resolver,
-                                       callback.callback(), &request);
-  EXPECT_EQ(ERR_IO_PENDING, rv);
-  EXPECT_EQ(OK, callback.WaitForResult());
-  EXPECT_TRUE(resolver);
-  return resolver.Pass();
-}
-
-class MockErrorObserver : public ProxyResolverErrorObserver {
+class MockBindings {
  public:
-  MockErrorObserver() : event_(true, false) {}
+  explicit MockBindings(HostResolver* host_resolver)
+      : host_resolver_(host_resolver), event_(true, false) {}
 
-  void OnPACScriptError(int line_number, const base::string16& error) override {
-    {
-      base::AutoLock l(lock_);
-      output += base::StringPrintf("Error: line %d: %s\n", line_number,
-                                   base::UTF16ToASCII(error).c_str());
-    }
+  void Alert(const base::string16& message) {
+    base::AutoLock l(lock_);
+    alerts_.push_back(base::UTF16ToASCII(message));
+  }
+  void OnError(int line_number, const base::string16& error) {
+    base::AutoLock l(lock_);
+    errors_.push_back(std::make_pair(line_number, base::UTF16ToASCII(error)));
     event_.Signal();
   }
 
-  std::string GetOutput() {
+  HostResolver* host_resolver() { return host_resolver_; }
+
+  std::vector<std::string> GetAlerts() {
+    base::AutoLock l(lock_);
+    return alerts_;
+  }
+
+  std::vector<std::pair<int, std::string>> GetErrors() {
     base::AutoLock l(lock_);
-    return output;
+    return errors_;
   }
 
-  void WaitForOutput() {
-    event_.Wait();
+  void WaitForError() { event_.Wait(); }
+
+  scoped_ptr<ProxyResolverV8Tracing::Bindings> CreateBindings() {
+    return make_scoped_ptr(new ForwardingBindings(this));
   }
 
  private:
+  class ForwardingBindings : public ProxyResolverV8Tracing::Bindings {
+   public:
+    ForwardingBindings(MockBindings* bindings) : bindings_(bindings) {}
+
+    // ProxyResolverV8Tracing::Bindings overrides.
+    void Alert(const base::string16& message) override {
+      bindings_->Alert(message);
+    }
+
+    void OnError(int line_number, const base::string16& error) override {
+      bindings_->OnError(line_number, error);
+    }
+
+    BoundNetLog GetBoundNetLog() override { return BoundNetLog(); }
+
+    HostResolver* GetHostResolver() override {
+      return bindings_->host_resolver();
+    }
+
+   private:
+    MockBindings* bindings_;
+  };
+
   base::Lock lock_;
-  std::string output;
+  std::vector<std::string> alerts_;
+  std::vector<std::pair<int, std::string>> errors_;
+  HostResolver* const host_resolver_;
 
   base::WaitableEvent event_;
 };
 
+scoped_ptr<ProxyResolverV8Tracing> CreateResolver(
+    scoped_ptr<ProxyResolverV8Tracing::Bindings> bindings,
+    const char* filename) {
+  scoped_ptr<ProxyResolverV8Tracing> resolver;
+  scoped_ptr<ProxyResolverV8TracingFactory> factory(
+      ProxyResolverV8TracingFactory::Create());
+  TestCompletionCallback callback;
+  scoped_ptr<ProxyResolverFactory::Request> request;
+  factory->CreateProxyResolverV8Tracing(LoadScriptData(filename),
+                                        bindings.Pass(), &resolver,
+                                        callback.callback(), &request);
+  EXPECT_EQ(OK, callback.WaitForResult());
+  EXPECT_TRUE(resolver);
+  return resolver.Pass();
+}
+
 TEST_F(ProxyResolverV8TracingTest, Simple) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      &log, &host_resolver, make_scoped_ptr(error_observer), "simple.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "simple.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback.WaitForResult());
 
   EXPECT_EQ("foo:99", proxy_info.proxy_server().ToURI());
 
   EXPECT_EQ(0u, host_resolver.num_resolve());
 
-  // There were no errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- nothing was logged.
-  EXPECT_EQ(0u, log.GetSize());
-  EXPECT_EQ(0u, request_log.GetSize());
+  // There were no alerts or errors.
+  EXPECT_TRUE(mock_bindings.GetAlerts().empty());
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
 }
 
 TEST_F(ProxyResolverV8TracingTest, JavascriptError) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      &log, &host_resolver, make_scoped_ptr(error_observer), "error.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "error.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://throw-an-error/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://throw-an-error/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(ERR_PAC_SCRIPT_FAILED, callback.WaitForResult());
 
   EXPECT_EQ(0u, host_resolver.num_resolve());
 
-  EXPECT_EQ("Error: line 5: Uncaught TypeError: Cannot read property 'split' "
-            "of null\n", error_observer->GetOutput());
-
-  // Check the NetLogs -- there was 1 alert and 1 javascript error, and they
-  // were output to both the global log, and per-request log.
-  TestNetLogEntry::List entries_list[2];
-  log.GetEntries(&entries_list[0]);
-  request_log.GetEntries(&entries_list[1]);
-
-  for (size_t list_i = 0; list_i < arraysize(entries_list); list_i++) {
-    const TestNetLogEntry::List& entries = entries_list[list_i];
-    EXPECT_EQ(2u, entries.size());
-    EXPECT_TRUE(
-        LogContainsEvent(entries, 0, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                         NetLog::PHASE_NONE));
-    EXPECT_TRUE(
-        LogContainsEvent(entries, 1, NetLog::TYPE_PAC_JAVASCRIPT_ERROR,
-                         NetLog::PHASE_NONE));
-
-    EXPECT_EQ("{\"message\":\"Prepare to DIE!\"}", entries[0].GetParamsJson());
-    EXPECT_EQ("{\"line_number\":5,\"message\":\"Uncaught TypeError: Cannot "
-              "read property 'split' of null\"}", entries[1].GetParamsJson());
-  }
+  // Check the output -- there was 1 alert and 1 javascript error.
+  ASSERT_EQ(1u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("Prepare to DIE!", mock_bindings.GetAlerts()[0]);
+  ASSERT_EQ(1u, mock_bindings.GetErrors().size());
+  EXPECT_EQ(5, mock_bindings.GetErrors()[0].first);
+  EXPECT_EQ("Uncaught TypeError: Cannot read property 'split' of null",
+            mock_bindings.GetErrors()[0].second);
 }
 
 TEST_F(ProxyResolverV8TracingTest, TooManyAlerts) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "too_many_alerts.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "too_many_alerts.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback.WaitForResult());
 
   // Iteration1 does a DNS resolve
@@ -220,45 +212,32 @@ TEST_F(ProxyResolverV8TracingTest, TooManyAlerts) {
   EXPECT_EQ(1u, host_resolver.num_resolve());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- the script generated 50 alerts, which were mirrored
-  // to both the global and per-request logs.
-  TestNetLogEntry::List entries_list[2];
-  log.GetEntries(&entries_list[0]);
-  request_log.GetEntries(&entries_list[1]);
-
-  for (size_t list_i = 0; list_i < arraysize(entries_list); list_i++) {
-    const TestNetLogEntry::List& entries = entries_list[list_i];
-    EXPECT_EQ(50u, entries.size());
-    for (size_t i = 0; i < entries.size(); ++i) {
-      ASSERT_TRUE(
-          LogContainsEvent(entries, i, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                           NetLog::PHASE_NONE));
-    }
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
+
+  // Check the alerts -- the script generated 50 alerts.
+  std::vector<std::string> alerts = mock_bindings.GetAlerts();
+  ASSERT_EQ(50u, alerts.size());
+  for (size_t i = 0; i < alerts.size(); i++) {
+    EXPECT_EQ("Gee, all these alerts are silly!", alerts[i]);
   }
 }
 
 // Verify that buffered alerts cannot grow unboundedly, even when the message is
 // empty string.
 TEST_F(ProxyResolverV8TracingTest, TooManyEmptyAlerts) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "too_many_empty_alerts.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver = CreateResolver(
+      mock_bindings.CreateBindings(), "too_many_empty_alerts.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback.WaitForResult());
 
   EXPECT_EQ("foo:3", proxy_info.proxy_server().ToURI());
@@ -266,22 +245,13 @@ TEST_F(ProxyResolverV8TracingTest, TooManyEmptyAlerts) {
   EXPECT_EQ(1u, host_resolver.num_resolve());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- the script generated 50 alerts, which were mirrored
-  // to both the global and per-request logs.
-  TestNetLogEntry::List entries_list[2];
-  log.GetEntries(&entries_list[0]);
-  request_log.GetEntries(&entries_list[1]);
-
-  for (size_t list_i = 0; list_i < arraysize(entries_list); list_i++) {
-    const TestNetLogEntry::List& entries = entries_list[list_i];
-    EXPECT_EQ(1000u, entries.size());
-    for (size_t i = 0; i < entries.size(); ++i) {
-      ASSERT_TRUE(
-          LogContainsEvent(entries, i, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                           NetLog::PHASE_NONE));
-    }
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
+
+  // Check the alerts -- the script generated 1000 alerts.
+  std::vector<std::string> alerts = mock_bindings.GetAlerts();
+  ASSERT_EQ(1000u, alerts.size());
+  for (size_t i = 0; i < alerts.size(); i++) {
+    EXPECT_EQ("", alerts[i]);
   }
 }
 
@@ -289,10 +259,8 @@ TEST_F(ProxyResolverV8TracingTest, TooManyEmptyAlerts) {
 // verifies the final result, and that the underlying DNS resolver received
 // the correct set of queries.
 TEST_F(ProxyResolverV8TracingTest, Dns) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRuleForAddressFamily(
       "host1", ADDRESS_FAMILY_IPV4, "166.155.144.44");
@@ -306,17 +274,16 @@ TEST_F(ProxyResolverV8TracingTest, Dns) {
       "*", ADDRESS_FAMILY_IPV4, "122.133.144.155");
   host_resolver.rules()->AddRule("*", "133.122.100.200");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      &log, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback.WaitForResult());
 
   // The test does 13 DNS resolution, however only 7 of them are unique.
@@ -341,48 +308,34 @@ TEST_F(ProxyResolverV8TracingTest, Dns) {
   EXPECT_EQ(kExpectedResult, proxy_info.proxy_server().ToURI());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- the script generated 1 alert, mirrored to both
-  // the per-request and global logs.
-  TestNetLogEntry::List entries_list[2];
-  log.GetEntries(&entries_list[0]);
-  request_log.GetEntries(&entries_list[1]);
-
-  for (size_t list_i = 0; list_i < arraysize(entries_list); list_i++) {
-    const TestNetLogEntry::List& entries = entries_list[list_i];
-    EXPECT_EQ(1u, entries.size());
-    EXPECT_TRUE(
-        LogContainsEvent(entries, 0, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                         NetLog::PHASE_NONE));
-    EXPECT_EQ("{\"message\":\"iteration: 7\"}", entries[0].GetParamsJson());
-  }
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
+
+  // The script generated 1 alert.
+  ASSERT_EQ(1u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("iteration: 7", mock_bindings.GetAlerts()[0]);
 }
 
 // This test runs a PAC script that does "myIpAddress()" followed by
 // "dnsResolve()". This requires 2 restarts. However once the HostResolver's
 // cache is warmed, subsequent calls should take 0 restarts.
 TEST_F(ProxyResolverV8TracingTest, DnsChecksCache) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("foopy", "166.155.144.11");
   host_resolver.rules()->AddRule("*", "122.133.144.155");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      &log, &host_resolver, make_scoped_ptr(error_observer), "simple_dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "simple_dns.js");
 
   TestCompletionCallback callback1;
   TestCompletionCallback callback2;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foopy/req1"), &proxy_info,
-                               callback1.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foopy/req1"), &proxy_info,
+                           callback1.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback1.WaitForResult());
 
   // The test does 2 DNS resolutions.
@@ -391,11 +344,10 @@ TEST_F(ProxyResolverV8TracingTest, DnsChecksCache) {
   // The first request took 2 restarts, hence on g_iteration=3.
   EXPECT_EQ("166.155.144.11:3", proxy_info.proxy_server().ToURI());
 
-  rv =
-      resolver->GetProxyForURL(GURL("http://foopy/req2"), &proxy_info,
-                               callback2.callback(), NULL, request_log.bound());
+  resolver->GetProxyForURL(GURL("http://foopy/req2"), &proxy_info,
+                           callback2.callback(), NULL,
+                           mock_bindings.CreateBindings());
 
-  EXPECT_EQ(ERR_IO_PENDING, rv);
   EXPECT_EQ(OK, callback2.WaitForResult());
 
   EXPECT_EQ(4u, host_resolver.num_resolve());
@@ -403,37 +355,31 @@ TEST_F(ProxyResolverV8TracingTest, DnsChecksCache) {
   // This time no restarts were required, so g_iteration incremented by 1.
   EXPECT_EQ("166.155.144.11:4", proxy_info.proxy_server().ToURI());
 
-  // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  EXPECT_EQ(0u, log.GetSize());
-  EXPECT_EQ(0u, request_log.GetSize());
+  // There were no alerts or errors.
+  EXPECT_TRUE(mock_bindings.GetAlerts().empty());
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
 }
 
 // This test runs a weird PAC script that was designed to defeat the DNS tracing
 // optimization. The proxy resolver should detect the inconsistency and
 // fall-back to synchronous mode execution.
 TEST_F(ProxyResolverV8TracingTest, FallBackToSynchronous1) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("host1", "166.155.144.11");
   host_resolver.rules()->AddRule("crazy4", "133.199.111.4");
   host_resolver.rules()->AddRule("*", "122.133.144.155");
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "global_sideffects1.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "global_sideffects1.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   // The script itself only does 2 DNS resolves per execution, however it
@@ -445,32 +391,18 @@ TEST_F(ProxyResolverV8TracingTest, FallBackToSynchronous1) {
             proxy_info.proxy_server().ToURI());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- the script generated 1 alert, mirrored to both
-  // the per-request and global logs.
-  TestNetLogEntry::List entries_list[2];
-  log.GetEntries(&entries_list[0]);
-  request_log.GetEntries(&entries_list[1]);
-
-  for (size_t list_i = 0; list_i < arraysize(entries_list); list_i++) {
-    const TestNetLogEntry::List& entries = entries_list[list_i];
-    EXPECT_EQ(1u, entries.size());
-    EXPECT_TRUE(
-        LogContainsEvent(entries, 0, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                         NetLog::PHASE_NONE));
-    EXPECT_EQ("{\"message\":\"iteration: 4\"}", entries[0].GetParamsJson());
-  }
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
+
+  ASSERT_EQ(1u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("iteration: 4", mock_bindings.GetAlerts()[0]);
 }
 
 // This test runs a weird PAC script that was designed to defeat the DNS tracing
 // optimization. The proxy resolver should detect the inconsistency and
 // fall-back to synchronous mode execution.
 TEST_F(ProxyResolverV8TracingTest, FallBackToSynchronous2) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("host1", "166.155.144.11");
   host_resolver.rules()->AddRule("host2", "166.155.144.22");
@@ -478,29 +410,24 @@ TEST_F(ProxyResolverV8TracingTest, FallBackToSynchronous2) {
   host_resolver.rules()->AddRule("host4", "166.155.144.44");
   host_resolver.rules()->AddRule("*", "122.133.144.155");
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "global_sideffects2.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "global_sideffects2.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   EXPECT_EQ(3u, host_resolver.num_resolve());
 
   EXPECT_EQ("166.155.144.44:100", proxy_info.proxy_server().ToURI());
 
-  // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  // Check the NetLogs -- nothing was logged.
-  EXPECT_EQ(0u, log.GetSize());
-  EXPECT_EQ(0u, request_log.GetSize());
+  // There were no alerts or errors.
+  EXPECT_TRUE(mock_bindings.GetAlerts().empty());
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
 }
 
 // This test runs a weird PAC script that yields a never ending sequence
@@ -508,25 +435,21 @@ TEST_F(ProxyResolverV8TracingTest, FallBackToSynchronous2) {
 // DNS resolves per request limit (20) after which every DNS resolve will
 // fail.
 TEST_F(ProxyResolverV8TracingTest, InfiniteDNSSequence) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("host*", "166.155.144.11");
   host_resolver.rules()->AddRule("*", "122.133.144.155");
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "global_sideffects3.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "global_sideffects3.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   EXPECT_EQ(20u, host_resolver.num_resolve());
@@ -540,11 +463,11 @@ TEST_F(ProxyResolverV8TracingTest, InfiniteDNSSequence) {
       "null:21", proxy_info.proxy_server().ToURI());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
 
-  // Check the NetLogs -- 1 alert was logged.
-  EXPECT_EQ(1u, log.GetSize());
-  EXPECT_EQ(1u, request_log.GetSize());
+  // 1 alert.
+  EXPECT_EQ(1u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("iteration: 21", mock_bindings.GetAlerts()[0]);
 }
 
 // This test runs a weird PAC script that yields a never ending sequence
@@ -552,25 +475,21 @@ TEST_F(ProxyResolverV8TracingTest, InfiniteDNSSequence) {
 // DNS resolves per request limit (20) after which every DNS resolve will
 // fail.
 TEST_F(ProxyResolverV8TracingTest, InfiniteDNSSequence2) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("host*", "166.155.144.11");
   host_resolver.rules()->AddRule("*", "122.133.144.155");
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "global_sideffects4.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "global_sideffects4.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   EXPECT_EQ(20u, host_resolver.num_resolve());
@@ -578,26 +497,23 @@ TEST_F(ProxyResolverV8TracingTest, InfiniteDNSSequence2) {
   EXPECT_EQ("null21:34", proxy_info.proxy_server().ToURI());
 
   // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
 
-  // Check the NetLogs -- 1 alert was logged.
-  EXPECT_EQ(1u, log.GetSize());
-  EXPECT_EQ(1u, request_log.GetSize());
+  // 1 alert.
+  EXPECT_EQ(1u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("iteration: 21", mock_bindings.GetAlerts()[0]);
 }
 
 void DnsDuringInitHelper(bool synchronous_host_resolver) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
+  MockBindings mock_bindings(&host_resolver);
   host_resolver.set_synchronous_mode(synchronous_host_resolver);
-  MockErrorObserver* error_observer = new MockErrorObserver;
 
   host_resolver.rules()->AddRule("host1", "91.13.12.1");
   host_resolver.rules()->AddRule("host2", "91.13.12.2");
 
-  scoped_ptr<ProxyResolver> resolver =
-      CreateResolver(&log, &host_resolver, make_scoped_ptr(error_observer),
-                     "dns_during_init.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns_during_init.js");
 
   // Initialization did 2 dnsResolves.
   EXPECT_EQ(2u, host_resolver.num_resolve());
@@ -611,10 +527,9 @@ void DnsDuringInitHelper(bool synchronous_host_resolver) {
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   // Fetched host1 and host2 again, since the ones done during initialization
@@ -624,21 +539,10 @@ void DnsDuringInitHelper(bool synchronous_host_resolver) {
   EXPECT_EQ("91.13.12.1-91.13.12.2-145.88.13.3-137.89.8.45:99",
             proxy_info.proxy_server().ToURI());
 
-  // Check the NetLogs -- the script generated 2 alerts during initialization.
-  EXPECT_EQ(0u, request_log.GetSize());
-  TestNetLogEntry::List entries;
-  log.GetEntries(&entries);
-
-  ASSERT_EQ(2u, entries.size());
-  EXPECT_TRUE(
-      LogContainsEvent(entries, 0, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                       NetLog::PHASE_NONE));
-  EXPECT_TRUE(
-      LogContainsEvent(entries, 1, NetLog::TYPE_PAC_JAVASCRIPT_ALERT,
-                       NetLog::PHASE_NONE));
-
-  EXPECT_EQ("{\"message\":\"Watsup\"}", entries[0].GetParamsJson());
-  EXPECT_EQ("{\"message\":\"Watsup2\"}", entries[1].GetParamsJson());
+  // 2 alerts.
+  ASSERT_EQ(2u, mock_bindings.GetAlerts().size());
+  EXPECT_EQ("Watsup", mock_bindings.GetAlerts()[0]);
+  EXPECT_EQ("Watsup2", mock_bindings.GetAlerts()[1]);
 }
 
 // Tests a PAC script which does DNS resolves during initialization.
@@ -660,22 +564,21 @@ void CrashCallback(int) {
 // times.
 TEST_F(ProxyResolverV8TracingTest, CancelAll) {
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddSimulatedFailure("*");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   const size_t kNumRequests = 5;
   ProxyInfo proxy_info[kNumRequests];
   ProxyResolver::RequestHandle request[kNumRequests];
 
   for (size_t i = 0; i < kNumRequests; ++i) {
-    int rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info[i],
-                                      base::Bind(&CrashCallback), &request[i],
-                                      BoundNetLog());
-    EXPECT_EQ(ERR_IO_PENDING, rv);
+    resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info[i],
+                             base::Bind(&CrashCallback), &request[i],
+                             mock_bindings.CreateBindings());
   }
 
   for (size_t i = 0; i < kNumRequests; ++i) {
@@ -688,12 +591,12 @@ TEST_F(ProxyResolverV8TracingTest, CancelAll) {
 // times.
 TEST_F(ProxyResolverV8TracingTest, CancelSome) {
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddSimulatedFailure("*");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   ProxyInfo proxy_info1;
   ProxyInfo proxy_info2;
@@ -701,14 +604,12 @@ TEST_F(ProxyResolverV8TracingTest, CancelSome) {
   ProxyResolver::RequestHandle request2;
   TestCompletionCallback callback;
 
-  int rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info1,
-                                    base::Bind(&CrashCallback), &request1,
-                                    BoundNetLog());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
-
-  rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info2,
-                                callback.callback(), &request2, BoundNetLog());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info1,
+                           base::Bind(&CrashCallback), &request1,
+                           mock_bindings.CreateBindings());
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info2,
+                           callback.callback(), &request2,
+                           mock_bindings.CreateBindings());
 
   resolver->CancelRequest(request1);
 
@@ -719,12 +620,12 @@ TEST_F(ProxyResolverV8TracingTest, CancelSome) {
 // posted a task the completion task back to origin thread.
 TEST_F(ProxyResolverV8TracingTest, CancelWhilePendingCompletionTask) {
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddSimulatedFailure("*");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "error.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "error.js");
 
   ProxyInfo proxy_info1;
   ProxyInfo proxy_info2;
@@ -734,18 +635,17 @@ TEST_F(ProxyResolverV8TracingTest, CancelWhilePendingCompletionTask) {
   ProxyResolver::RequestHandle request3;
   TestCompletionCallback callback;
 
-  int rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info1,
-                                    base::Bind(&CrashCallback), &request1,
-                                    BoundNetLog());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info1,
+                           base::Bind(&CrashCallback), &request1,
+                           mock_bindings.CreateBindings());
 
-  rv = resolver->GetProxyForURL(GURL("http://throw-an-error/"), &proxy_info2,
-                                callback.callback(), &request2, BoundNetLog());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://throw-an-error"), &proxy_info2,
+                           callback.callback(), &request2,
+                           mock_bindings.CreateBindings());
 
   // Wait until the first request has finished running on the worker thread.
   // (The second request will output an error).
-  error_observer->WaitForOutput();
+  mock_bindings.WaitForError();
 
   // Cancel the first request, while it has a pending completion task on
   // the origin thread.
@@ -754,10 +654,9 @@ TEST_F(ProxyResolverV8TracingTest, CancelWhilePendingCompletionTask) {
   EXPECT_EQ(ERR_PAC_SCRIPT_FAILED, callback.WaitForResult());
 
   // Start another request, to make sure it is able to complete.
-  rv = resolver->GetProxyForURL(GURL("http://i-have-no-idea-what-im-doing/"),
-                                &proxy_info3, callback.callback(), &request3,
-                                BoundNetLog());
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://i-have-no-idea-what-im-doing/"),
+                           &proxy_info3, callback.callback(), &request3,
+                           mock_bindings.CreateBindings());
 
   EXPECT_EQ(OK, callback.WaitForResult());
 
@@ -836,29 +735,25 @@ class BlockableHostResolver : public HostResolver {
 // when the request has an outstanding DNS request in flight.
 TEST_F(ProxyResolverV8TracingTest, CancelWhileOutstandingNonBlockingDns) {
   BlockableHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   ProxyInfo proxy_info1;
   ProxyInfo proxy_info2;
   ProxyResolver::RequestHandle request1;
   ProxyResolver::RequestHandle request2;
 
-  int rv = resolver->GetProxyForURL(GURL("http://foo/req1"), &proxy_info1,
-                                    base::Bind(&CrashCallback), &request1,
-                                    BoundNetLog());
-
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/req1"), &proxy_info1,
+                           base::Bind(&CrashCallback), &request1,
+                           mock_bindings.CreateBindings());
 
   host_resolver.WaitUntilRequestIsReceived();
 
-  rv = resolver->GetProxyForURL(GURL("http://foo/req2"), &proxy_info2,
-                                base::Bind(&CrashCallback), &request2,
-                                BoundNetLog());
-
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/req2"), &proxy_info2,
+                           base::Bind(&CrashCallback), &request2,
+                           mock_bindings.CreateBindings());
 
   host_resolver.WaitUntilRequestIsReceived();
 
@@ -872,7 +767,7 @@ TEST_F(ProxyResolverV8TracingTest, CancelWhileOutstandingNonBlockingDns) {
   // should have been cancelled.
 }
 
-void CancelRequestAndPause(ProxyResolver* resolver,
+void CancelRequestAndPause(ProxyResolverV8Tracing* resolver,
                            ProxyResolver::RequestHandle request) {
   resolver->CancelRequest(request);
 
@@ -887,19 +782,17 @@ void CancelRequestAndPause(ProxyResolver* resolver,
 // cancellation while the worker thread is waiting on this event.
 TEST_F(ProxyResolverV8TracingTest, CancelWhileBlockedInNonBlockingDns) {
   BlockableHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   ProxyInfo proxy_info;
   ProxyResolver::RequestHandle request;
 
-  int rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                                    base::Bind(&CrashCallback), &request,
-                                    BoundNetLog());
-
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           base::Bind(&CrashCallback), &request,
+                           mock_bindings.CreateBindings());
 
   host_resolver.SetAction(
       base::Bind(CancelRequestAndPause, resolver.get(), request));
@@ -916,19 +809,17 @@ TEST_F(ProxyResolverV8TracingTest, CancelWhileBlockedInNonBlockingDns) {
 // the request is sent to the host resolver.
 TEST_F(ProxyResolverV8TracingTest, CancelWhileBlockedInNonBlockingDns2) {
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      nullptr, &host_resolver, make_scoped_ptr(error_observer), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "dns.js");
 
   ProxyInfo proxy_info;
   ProxyResolver::RequestHandle request;
 
-  int rv = resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
-                                    base::Bind(&CrashCallback), &request,
-                                    BoundNetLog());
-
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foo/"), &proxy_info,
+                           base::Bind(&CrashCallback), &request,
+                           mock_bindings.CreateBindings());
 
   // Wait a bit, so the DNS task has hopefully been posted. The test will
   // work whatever the delay is here, but it is most useful if the delay
@@ -942,19 +833,15 @@ TEST_F(ProxyResolverV8TracingTest, CancelWhileBlockedInNonBlockingDns2) {
 TEST_F(ProxyResolverV8TracingTest,
        CancelCreateResolverWhileOutstandingBlockingDns) {
   BlockableHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  ProxyResolverFactoryV8Tracing factory(
-      &host_resolver, nullptr, ProxyResolver::LoadStateChangedCallback(),
-      base::Bind(&ReturnErrorObserver,
-                 base::Passed(make_scoped_ptr(error_observer))));
-
-  scoped_ptr<ProxyResolver> resolver;
+  scoped_ptr<ProxyResolverV8TracingFactory> factory(
+      ProxyResolverV8TracingFactory::Create());
+  scoped_ptr<ProxyResolverV8Tracing> resolver;
   scoped_ptr<ProxyResolverFactory::Request> request;
-  int rv = factory.CreateProxyResolver(LoadScriptData("dns_during_init.js"),
-                                       &resolver, base::Bind(&CrashCallback),
-                                       &request);
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  factory->CreateProxyResolverV8Tracing(
+      LoadScriptData("dns_during_init.js"), mock_bindings.CreateBindings(),
+      &resolver, base::Bind(&CrashCallback), &request);
 
   host_resolver.WaitUntilRequestIsReceived();
 
@@ -964,20 +851,17 @@ TEST_F(ProxyResolverV8TracingTest,
 
 TEST_F(ProxyResolverV8TracingTest, DeleteFactoryWhileOutstandingBlockingDns) {
   BlockableHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  scoped_ptr<ProxyResolver> resolver;
+  scoped_ptr<ProxyResolverV8Tracing> resolver;
   scoped_ptr<ProxyResolverFactory::Request> request;
   {
-    ProxyResolverFactoryV8Tracing factory(
-        &host_resolver, nullptr, ProxyResolver::LoadStateChangedCallback(),
-        base::Bind(&ReturnErrorObserver,
-                   base::Passed(make_scoped_ptr(error_observer))));
-
-    int rv = factory.CreateProxyResolver(LoadScriptData("dns_during_init.js"),
-                                         &resolver, base::Bind(&CrashCallback),
-                                         &request);
-    EXPECT_EQ(ERR_IO_PENDING, rv);
+    scoped_ptr<ProxyResolverV8TracingFactory> factory(
+        ProxyResolverV8TracingFactory::Create());
+
+    factory->CreateProxyResolverV8Tracing(
+        LoadScriptData("dns_during_init.js"), mock_bindings.CreateBindings(),
+        &resolver, base::Bind(&CrashCallback), &request);
     host_resolver.WaitUntilRequestIsReceived();
   }
   EXPECT_EQ(1, host_resolver.num_cancelled_requests());
@@ -985,20 +869,17 @@ TEST_F(ProxyResolverV8TracingTest, DeleteFactoryWhileOutstandingBlockingDns) {
 
 TEST_F(ProxyResolverV8TracingTest, ErrorLoadingScript) {
   BlockableHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
-  ProxyResolverFactoryV8Tracing factory(
-      &host_resolver, nullptr, ProxyResolver::LoadStateChangedCallback(),
-      base::Bind(&ReturnErrorObserver,
-                 base::Passed(make_scoped_ptr(error_observer))));
-
-  scoped_ptr<ProxyResolver> resolver;
+  scoped_ptr<ProxyResolverV8TracingFactory> factory(
+      ProxyResolverV8TracingFactory::Create());
+  scoped_ptr<ProxyResolverV8Tracing> resolver;
   scoped_ptr<ProxyResolverFactory::Request> request;
   TestCompletionCallback callback;
-  int rv =
-      factory.CreateProxyResolver(LoadScriptData("error_on_load.js"), &resolver,
-                                  callback.callback(), &request);
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  factory->CreateProxyResolverV8Tracing(
+      LoadScriptData("error_on_load.js"), mock_bindings.CreateBindings(),
+      &resolver, callback.callback(), &request);
+
   EXPECT_EQ(ERR_PAC_SCRIPT_FAILED, callback.WaitForResult());
   EXPECT_FALSE(resolver);
 }
@@ -1006,25 +887,21 @@ TEST_F(ProxyResolverV8TracingTest, ErrorLoadingScript) {
 // This tests that the execution of a PAC script is terminated when the DNS
 // dependencies are missing. If the test fails, then it will hang.
 TEST_F(ProxyResolverV8TracingTest, Terminate) {
-  TestNetLog log;
-  BoundTestNetLog request_log;
   MockCachingHostResolver host_resolver;
-  MockErrorObserver* error_observer = new MockErrorObserver;
+  MockBindings mock_bindings(&host_resolver);
 
   host_resolver.rules()->AddRule("host1", "182.111.0.222");
   host_resolver.rules()->AddRule("host2", "111.33.44.55");
 
-  scoped_ptr<ProxyResolver> resolver = CreateResolver(
-      &log, &host_resolver, make_scoped_ptr(error_observer), "terminate.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver =
+      CreateResolver(mock_bindings.CreateBindings(), "terminate.js");
 
   TestCompletionCallback callback;
   ProxyInfo proxy_info;
 
-  int rv =
-      resolver->GetProxyForURL(GURL("http://foopy/req1"), &proxy_info,
-                               callback.callback(), NULL, request_log.bound());
-
-  EXPECT_EQ(ERR_IO_PENDING, rv);
+  resolver->GetProxyForURL(GURL("http://foopy/req1"), &proxy_info,
+                           callback.callback(), NULL,
+                           mock_bindings.CreateBindings());
   EXPECT_EQ(OK, callback.WaitForResult());
 
   // The test does 2 DNS resolutions.
@@ -1032,11 +909,9 @@ TEST_F(ProxyResolverV8TracingTest, Terminate) {
 
   EXPECT_EQ("foopy:3", proxy_info.proxy_server().ToURI());
 
-  // No errors.
-  EXPECT_EQ("", error_observer->GetOutput());
-
-  EXPECT_EQ(0u, log.GetSize());
-  EXPECT_EQ(0u, request_log.GetSize());
+  // No errors or alerts.
+  EXPECT_TRUE(mock_bindings.GetErrors().empty());
+  EXPECT_TRUE(mock_bindings.GetAlerts().empty());
 }
 
 // Tests that multiple instances of ProxyResolverV8Tracing can coexist and run
@@ -1048,6 +923,7 @@ TEST_F(ProxyResolverV8TracingTest, MultipleResolvers) {
   // Setup resolver0
   // ------------------------
   MockHostResolver host_resolver0;
+  MockBindings mock_bindings0(&host_resolver0);
   host_resolver0.rules()->AddRuleForAddressFamily(
       "host1", ADDRESS_FAMILY_IPV4, "166.155.144.44");
   host_resolver0.rules()
@@ -1059,38 +935,35 @@ TEST_F(ProxyResolverV8TracingTest, MultipleResolvers) {
   host_resolver0.rules()->AddRuleForAddressFamily(
       "*", ADDRESS_FAMILY_IPV4, "122.133.144.155");
   host_resolver0.rules()->AddRule("*", "133.122.100.200");
-  scoped_ptr<ProxyResolver> resolver0 =
-      CreateResolver(nullptr, &host_resolver0,
-                     make_scoped_ptr(new MockErrorObserver), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver0 =
+      CreateResolver(mock_bindings0.CreateBindings(), "dns.js");
 
   // ------------------------
   // Setup resolver1
   // ------------------------
-  scoped_ptr<ProxyResolver> resolver1 =
-      CreateResolver(nullptr, &host_resolver0,
-                     make_scoped_ptr(new MockErrorObserver), "dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver1 =
+      CreateResolver(mock_bindings0.CreateBindings(), "dns.js");
 
   // ------------------------
   // Setup resolver2
   // ------------------------
-  scoped_ptr<ProxyResolver> resolver2 =
-      CreateResolver(nullptr, &host_resolver0,
-                     make_scoped_ptr(new MockErrorObserver), "simple.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver2 =
+      CreateResolver(mock_bindings0.CreateBindings(), "simple.js");
 
   // ------------------------
   // Setup resolver3
   // ------------------------
   MockHostResolver host_resolver3;
+  MockBindings mock_bindings3(&host_resolver3);
   host_resolver3.rules()->AddRule("foo", "166.155.144.33");
-  scoped_ptr<ProxyResolver> resolver3 =
-      CreateResolver(nullptr, &host_resolver3,
-                     make_scoped_ptr(new MockErrorObserver), "simple_dns.js");
+  scoped_ptr<ProxyResolverV8Tracing> resolver3 =
+      CreateResolver(mock_bindings3.CreateBindings(), "simple_dns.js");
 
   // ------------------------
   // Queue up work for each resolver (which will be running in parallel).
   // ------------------------
 
-  ProxyResolver* resolver[] = {
+  ProxyResolverV8Tracing* resolver[] = {
       resolver0.get(), resolver1.get(), resolver2.get(), resolver3.get(),
   };
 
@@ -1102,10 +975,10 @@ TEST_F(ProxyResolverV8TracingTest, MultipleResolvers) {
 
   for (size_t i = 0; i < kNumResults; ++i) {
     size_t resolver_i = i % kNumResolvers;
-    int rv = resolver[resolver_i]->GetProxyForURL(
+    resolver[resolver_i]->GetProxyForURL(
         GURL("http://foo/"), &proxy_info[i], callback[i].callback(), NULL,
-        BoundNetLog());
-    EXPECT_EQ(ERR_IO_PENDING, rv);
+        resolver_i == 3 ? mock_bindings3.CreateBindings()
+                        : mock_bindings0.CreateBindings());
   }
 
   // ------------------------