Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/mime_sniffing_resource_handler_unittest.cc

Index: content/browser/loader/mime_sniffing_resource_handler_unittest.cc
diff --git a/content/browser/loader/mime_sniffing_resource_handler_unittest.cc b/content/browser/loader/mime_sniffing_resource_handler_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..61b22bb5e6f4a132a966b54086071c92ae84d017
--- /dev/null
+++ b/content/browser/loader/mime_sniffing_resource_handler_unittest.cc
@@ -0,0 +1,1013 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/loader/mime_sniffing_resource_handler.h"
+
+#include <stdint.h>
+
+#include <memory>
+
+#include "base/files/file_path.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "content/browser/loader/intercepting_resource_handler.h"
+#include "content/browser/loader/resource_dispatcher_host_impl.h"
+#include "content/public/browser/resource_controller.h"
+#include "content/public/browser/resource_dispatcher_host_delegate.h"
+#include "content/public/browser/resource_request_info.h"
+#include "content/public/common/resource_response.h"
+#include "content/public/common/webplugininfo.h"
+#include "content/public/test/test_browser_thread_bundle.h"
+#include "content/public/test/test_utils.h"
+#include "content/test/fake_plugin_service.h"
+#include "net/url_request/url_request_context.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+namespace content {
+
+namespace {
+
+class TestResourceHandler : public ResourceHandler {
+ public:
+  TestResourceHandler(bool response_started_succeeds,
+                      bool defer_on_response_started,
+                      bool will_read_succeeds,
+                      bool read_completed_succeeds,
+                      bool defer_on_read_completed)
+      : ResourceHandler(nullptr),
+        buffer_(new net::IOBuffer(2048)),
+        response_started_succeeds_(response_started_succeeds),
+        defer_on_response_started_(defer_on_response_started),
+        will_read_succeeds_(will_read_succeeds),
+        read_completed_succeeds_(read_completed_succeeds),
+        defer_on_read_completed_(defer_on_read_completed),
+        on_will_start_called_(0),
+        on_request_redirected_called_(0),
+        on_response_started_called_(0),
+        on_will_read_called_(0),
+        on_read_completed_called_(0) {}
+
+  void SetController(ResourceController* controller) override {}
+
+  bool OnRequestRedirected(const net::RedirectInfo& redirect_info,
+                           ResourceResponse* response,
+                           bool* defer) override {
+    on_request_redirected_called_++;
+    NOTREACHED();
+    return false;
+  }
+
+  bool OnResponseStarted(ResourceResponse* response, bool* defer) override {
+    on_response_started_called_++;
+    if (defer_on_response_started_)
+      *defer = true;
+    return response_started_succeeds_;
+  }
+
+  bool OnWillStart(const GURL& url, bool* defer) override {
+    on_will_start_called_++;
+    return false;
+  }
+
+  bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                  int* buf_size,
+                  int min_size) override {
+    on_will_read_called_++;
+    *buf = buffer_;
+    *buf_size = 2048;
+    return will_read_succeeds_;
+  }
+
+  bool OnReadCompleted(int bytes_read, bool* defer) override {
+    DCHECK_LT(bytes_read, 2048);
+    on_read_completed_called_++;
+    if (defer_on_read_completed_)
+      *defer = true;
+    return read_completed_succeeds_;
+  }
+
+  void OnResponseCompleted(const net::URLRequestStatus& status,
+                           const std::string& security_info,
+                           bool* defer) override {}
+
+  void OnDataDownloaded(int bytes_downloaded) override { NOTREACHED(); }
+
+  scoped_refptr<net::IOBuffer> buffer() { return buffer_; }
+
+  int on_will_start_called() const { return on_will_start_called_; }
+  int on_request_redirected_called() const {
+    return on_request_redirected_called_;
+  }
+  int on_response_started_called() const { return on_response_started_called_; }
+  int on_will_read_called() const { return on_will_read_called_; }
+  int on_read_completed_called() const { return on_read_completed_called_; }
+
+ private:
+  scoped_refptr<net::IOBuffer> buffer_;
+  bool response_started_succeeds_;
+  bool defer_on_response_started_;
+  bool will_read_succeeds_;
+  bool read_completed_succeeds_;
+  bool defer_on_read_completed_;
+
+  int on_will_start_called_;
+  int on_request_redirected_called_;
+  int on_response_started_called_;
+  int on_will_read_called_;
+  int on_read_completed_called_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestResourceHandler);
+};
+
+class TestResourceDispatcherHostDelegate
+    : public ResourceDispatcherHostDelegate {
+ public:
+  explicit TestResourceDispatcherHostDelegate(bool must_download)
+      : must_download_(must_download) {}
+
+  bool ShouldForceDownloadResource(const GURL& url,
+                                   const std::string& mime_type) override {
+    return must_download_;
+  }
+
+ private:
+  const bool must_download_;
+};
+
+class TestResourceDispatcherHost : public ResourceDispatcherHostImpl {
+ public:
+  explicit TestResourceDispatcherHost(bool stream_has_handler)
+      : stream_has_handler_(stream_has_handler),
+        intercepted_as_stream_(false),
+        intercepted_as_stream_count_(0),
+        new_resource_handler_(nullptr) {}
+
+  bool intercepted_as_stream() const { return intercepted_as_stream_; }
+
+  std::unique_ptr<ResourceHandler> CreateResourceHandlerForDownload(
+      net::URLRequest* request,
+      bool is_content_initiated,
+      bool must_download) override {
+    return CreateNewResourceHandler();
+  }
+
+  std::unique_ptr<ResourceHandler> MaybeInterceptAsStream(
+      const base::FilePath& plugin_path,
+      net::URLRequest* request,
+      ResourceResponse* response,
+      std::string* payload) override {
+    intercepted_as_stream_count_++;
+    if (stream_has_handler_)
+      intercepted_as_stream_ = true;
+    return CreateNewResourceHandler();
+  }
+
+  int intercepted_as_stream_count() const {
+    return intercepted_as_stream_count_;
+  }
+
+  TestResourceHandler* new_resource_handler() const {
+    return new_resource_handler_;
+  }
+
+ private:
+  std::unique_ptr<ResourceHandler> CreateNewResourceHandler() {
+    std::unique_ptr<TestResourceHandler> new_resource_handler(
+        new TestResourceHandler(false, false, true, true, false));
+    new_resource_handler_ = new_resource_handler.get();
+    return std::move(new_resource_handler);
+  }
+
+  // Whether the URL request should be intercepted as a stream.
+  bool stream_has_handler_;
+
+  // Whether the URL request has been intercepted as a stream.
+  bool intercepted_as_stream_;
+
+  // Count of number of times MaybeInterceptAsStream function get called in a
+  // test.
+  int intercepted_as_stream_count_;
+
+  // The last alternative TestResourceHandler created by this
+  // TestResourceDispatcherHost.
+  TestResourceHandler* new_resource_handler_;
+};
+
+class TestFakePluginService : public FakePluginService {
+ public:
+  // If |is_plugin_stale| is true, GetPluginInfo will indicate the plugins are
+  // stale until GetPlugins is called.
+  TestFakePluginService(bool plugin_available, bool is_plugin_stale)
+      : plugin_available_(plugin_available),
+        is_plugin_stale_(is_plugin_stale) {}
+
+  bool GetPluginInfo(int render_process_id,
+                     int render_frame_id,
+                     ResourceContext* context,
+                     const GURL& url,
+                     const GURL& page_url,
+                     const std::string& mime_type,
+                     bool allow_wildcard,
+                     bool* is_stale,
+                     WebPluginInfo* info,
+                     std::string* actual_mime_type) override {
+    *is_stale = is_plugin_stale_;
+    if (!is_plugin_stale_ || !plugin_available_)
+      return false;
+    info->type = WebPluginInfo::PLUGIN_TYPE_BROWSER_PLUGIN;
+    info->path = base::FilePath::FromUTF8Unsafe(
+        std::string("chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/"));
+    return true;
+  }
+
+  void GetPlugins(const GetPluginsCallback& callback) override {
+    is_plugin_stale_ = false;
+    std::vector<WebPluginInfo> plugins;
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, plugins));
+  }
+
+ private:
+  const bool plugin_available_;
+  bool is_plugin_stale_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestFakePluginService);
+};
+
+class TestResourceController : public ResourceController {
+ public:
+  TestResourceController() : cancel_call_count_(0), resume_call_count_(0) {}
+
+  void Cancel() override { cancel_call_count_++; }
+
+  void CancelAndIgnore() override { NOTREACHED(); }
+
+  void CancelWithError(int error_code) override { NOTREACHED(); }
+
+  void Resume() override { resume_call_count_++; }
+
+  int cancel_call_count() const { return cancel_call_count_; }
+  int resume_call_count() const { return resume_call_count_; }
+
+ private:
+  int cancel_call_count_;
+  int resume_call_count_;
+};
+
+}  // namespace
+
+class MimeSniffingResourceHandlerTest : public testing::Test {
+ public:
+  MimeSniffingResourceHandlerTest()
+      : stream_has_handler_(false),
+        plugin_available_(false),
+        plugin_stale_(false) {}
+
+  // Tests that the MimeSniffingHandler properly sets the accept field in the
+  // header. Returns the accept header value.
+  std::string TestAcceptHeaderSetting(ResourceType request_resource_type);
+  std::string TestAcceptHeaderSettingWithURLRequest(
+      ResourceType request_resource_type,
+      net::URLRequest* request);
+
+  void set_stream_has_handler(bool stream_has_handler) {
+    stream_has_handler_ = stream_has_handler;
+  }
+
+  void set_plugin_available(bool plugin_available) {
+    plugin_available_ = plugin_available;
+  }
+
+  void set_plugin_stale(bool plugin_stale) { plugin_stale_ = plugin_stale; }
+
+  bool TestStreamIsIntercepted(bool allow_download,
+                               bool must_download,
+                               ResourceType request_resource_type);
+
+  // Tests the operation of the MimeSniffingHandler when it needs to buffer
+  // data (example case: the response is text/plain).
+  void TestHandlerSniffing(bool response_started,
+                           bool defer_response_started,
+                           bool will_read,
+                           bool read_completed,
+                           bool defer_read_completed);
+
+  // Tests the operation of the MimeSniffingHandler when it doesn't buffer
+  // data (example case: the response is text/html).
+  void TestHandlerNoSniffing(bool response_started,
+                             bool defer_response_started,
+                             bool will_read,
+                             bool read_completed,
+                             bool defer_read_completed);
+
+ private:
+  // Whether the URL request should be intercepted as a stream.
+  bool stream_has_handler_;
+  bool plugin_available_;
+  bool plugin_stale_;
+
+  TestBrowserThreadBundle thread_bundle_;
+};
+
+std::string MimeSniffingResourceHandlerTest::TestAcceptHeaderSetting(
+    ResourceType request_resource_type) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  return TestAcceptHeaderSettingWithURLRequest(request_resource_type,
+                                               request.get());
+}
+
+std::string
+MimeSniffingResourceHandlerTest::TestAcceptHeaderSettingWithURLRequest(
+    ResourceType request_resource_type,
+    net::URLRequest* request) {
+  bool is_main_frame = request_resource_type == RESOURCE_TYPE_MAIN_FRAME;
+  ResourceRequestInfo::AllocateForTesting(request, request_resource_type,
+                                          nullptr,        // context
+                                          0,              // render_process_id
+                                          0,              // render_view_id
+                                          0,              // render_frame_id
+                                          is_main_frame,  // is_main_frame
+                                          false,   // parent_is_main_frame
+                                          false,   // allow_download
+                                          true,    // is_async
+                                          false);  // is_using_lofi
+
+  std::unique_ptr<ResourceHandler> mime_sniffing_handler(
+      new MimeSniffingResourceHandler(
+          std::unique_ptr<ResourceHandler>(
+              new TestResourceHandler(false, false, false, false, false)),
+          nullptr, nullptr, nullptr, request));
+
+  bool defer = false;
+  mime_sniffing_handler->OnWillStart(request->url(), &defer);
+  content::RunAllPendingInMessageLoop();
+
+  std::string accept_header;
+  request->extra_request_headers().GetHeader("Accept", &accept_header);
+  return accept_header;
+}
+
+bool MimeSniffingResourceHandlerTest::TestStreamIsIntercepted(
+    bool allow_download,
+    bool must_download,
+    ResourceType request_resource_type) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  bool is_main_frame = request_resource_type == RESOURCE_TYPE_MAIN_FRAME;
+  ResourceRequestInfo::AllocateForTesting(request.get(), request_resource_type,
+                                          nullptr,        // context
+                                          0,              // render_process_id
+                                          0,              // render_view_id
+                                          0,              // render_frame_id
+                                          is_main_frame,  // is_main_frame
+                                          false,  // parent_is_main_frame
+                                          allow_download,  // allow_download
+                                          true,            // is_async
+                                          false);          // is_using_lofi
+
+  TestResourceDispatcherHost host(stream_has_handler_);
+  TestResourceDispatcherHostDelegate host_delegate(must_download);
+  host.SetDelegate(&host_delegate);
+
+  TestFakePluginService plugin_service(plugin_available_, plugin_stale_);
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::unique_ptr<ResourceHandler>(),
+                                      nullptr));
+  std::unique_ptr<ResourceHandler> mime_handler(new MimeSniffingResourceHandler(
+      std::unique_ptr<ResourceHandler>(
+          new TestResourceHandler(false, false, false, false, false)),
+      &host, &plugin_service, intercepting_handler.get(), request.get()));
+
+  TestResourceController resource_controller;
+  mime_handler->SetController(&resource_controller);
+
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+  // The MIME type isn't important but it shouldn't be empty.
+  response->head.mime_type = "application/pdf";
+
+  bool defer = false;
+  mime_handler->OnResponseStarted(response.get(), &defer);
+
+  content::RunAllPendingInMessageLoop();
+  EXPECT_LT(host.intercepted_as_stream_count(), 2);
+  if (allow_download)
+    EXPECT_TRUE(intercepting_handler->new_handler_for_testing());
+  return host.intercepted_as_stream();
+}
+
+void MimeSniffingResourceHandlerTest::TestHandlerSniffing(
+    bool response_started,
+    bool defer_response_started,
+    bool will_read,
+    bool read_completed,
+    bool defer_read_completed) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          false,    // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  TestResourceDispatcherHost host(false);
+  TestResourceDispatcherHostDelegate host_delegate(false);
+  host.SetDelegate(&host_delegate);
+
+  TestFakePluginService plugin_service(plugin_available_, plugin_stale_);
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::unique_ptr<ResourceHandler>(),
+                                      nullptr));
+  std::unique_ptr<TestResourceHandler> scoped_test_handler =
+      std::unique_ptr<TestResourceHandler>(new TestResourceHandler(
+          response_started, defer_response_started, will_read, read_completed,
+          defer_read_completed));
+  TestResourceHandler* test_handler = scoped_test_handler.get();
+  std::unique_ptr<MimeSniffingResourceHandler> mime_sniffing_handler(
+      new MimeSniffingResourceHandler(
+          std::move(scoped_test_handler), &host, &plugin_service,
+          intercepting_handler.get(), request.get()));
+
+  TestResourceController resource_controller;
+  mime_sniffing_handler->SetController(&resource_controller);
+
+  bool defer = false;
+  mime_sniffing_handler->OnWillStart(GURL(), &defer);
+
+  // The response should be sniffed.
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+  response->head.mime_type.assign("text/plain");
+
+  // Simulate the response starting. The MimeSniffingHandler should start
+  // buffering, so the return value should always be true.
+  EXPECT_TRUE(mime_sniffing_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+  EXPECT_EQ(0, resource_controller.resume_call_count());
+  EXPECT_FALSE(defer);
+
+  // Read some data to sniff the mime type. This will ask the next
+  // ResourceHandler for a buffer.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  EXPECT_EQ(will_read,
+            mime_sniffing_handler->OnWillRead(&read_buffer, &buf_size, -1));
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+  if (!will_read) {
+    EXPECT_EQ(1, test_handler->on_will_start_called());
+    EXPECT_EQ(0, test_handler->on_request_redirected_called());
+    EXPECT_EQ(0, test_handler->on_response_started_called());
+    EXPECT_EQ(1, test_handler->on_will_read_called());
+    EXPECT_EQ(0, test_handler->on_read_completed_called());
+
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  // Simulate an HTML page. The mime sniffer will identify the MimeType and
+  // proceed with replay.
+  char data[] = "!DOCTYPE html\n<head>\n<title>Foo</title>\n</head>";
+  memcpy(read_buffer->data(), data, sizeof(data));
+
+  defer = false;
+  bool return_value =
+      mime_sniffing_handler->OnReadCompleted(sizeof(data), &defer);
+
+  // If the next handler cancels the response start, the caller of
+  // MimeSniffingHandler::OnReadCompleted should be notified immediately.
+  if (!response_started) {
+    EXPECT_FALSE(defer);
+    EXPECT_EQ(response_started, return_value);
+    EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+    EXPECT_EQ(1, test_handler->on_will_start_called());
+    EXPECT_EQ(0, test_handler->on_request_redirected_called());
+    EXPECT_EQ(1, test_handler->on_response_started_called());
+    EXPECT_EQ(1, test_handler->on_will_read_called());
+    EXPECT_EQ(0, test_handler->on_read_completed_called());
+
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  // The replay can be deferred both at response started and read replay
+  // stages.
+  EXPECT_EQ(defer, defer_response_started || defer_read_completed);
+  if (defer_response_started) {
+    EXPECT_TRUE(defer);
+    EXPECT_TRUE(return_value);
+    EXPECT_EQ(MimeSniffingResourceHandler::STATE_REPLAYING_RESPONSE_RECEIVED,
+              mime_sniffing_handler->state_);
+    mime_sniffing_handler->Resume();
+  }
+
+  // The body that was sniffed should be transmitted to the next handler. This
+  // may cancel the request.
+  if (!read_completed) {
+    if (defer_response_started) {
+      EXPECT_EQ(1, resource_controller.cancel_call_count());
+    } else {
+      EXPECT_EQ(0, resource_controller.cancel_call_count());
+      EXPECT_FALSE(return_value);
+    }
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  EXPECT_EQ(MimeSniffingResourceHandler::STATE_STREAMING,
+            mime_sniffing_handler->state_);
+
+  // The request may be deferred by the next handler once the read is done.
+  if (defer_read_completed) {
+    EXPECT_TRUE(defer);
+    mime_sniffing_handler->Resume();
+  }
+
+  EXPECT_EQ(MimeSniffingResourceHandler::STATE_STREAMING,
+            mime_sniffing_handler->state_);
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+  // Even if the next handler defers the request twice, the
+  // MimeSniffingResourceHandler should only call Resume on its controller
+  // once.
+  if (defer_response_started || defer_read_completed) {
+    EXPECT_EQ(1, resource_controller.resume_call_count());
+  } else {
+    EXPECT_EQ(0, resource_controller.resume_call_count());
+  }
+
+  EXPECT_EQ(1, test_handler->on_will_start_called());
+  EXPECT_EQ(0, test_handler->on_request_redirected_called());
+  EXPECT_EQ(1, test_handler->on_response_started_called());
+  EXPECT_EQ(1, test_handler->on_will_read_called());
+  EXPECT_EQ(1, test_handler->on_read_completed_called());
+
+  // Process all messages to ensure proper test teardown.
+  content::RunAllPendingInMessageLoop();
+}
+
+void MimeSniffingResourceHandlerTest::TestHandlerNoSniffing(
+    bool response_started,
+    bool defer_response_started,
+    bool will_read,
+    bool read_completed,
+    bool defer_read_completed) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          false,    // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  TestResourceDispatcherHost host(false);
+  TestResourceDispatcherHostDelegate host_delegate(false);
+  host.SetDelegate(&host_delegate);
+
+  TestFakePluginService plugin_service(plugin_available_, plugin_stale_);
+  std::unique_ptr<InterceptingResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::unique_ptr<ResourceHandler>(),
+                                      nullptr));
+
+  std::unique_ptr<TestResourceHandler> scoped_test_handler =
+      std::unique_ptr<TestResourceHandler>(new TestResourceHandler(
+          response_started, defer_response_started, will_read, read_completed,
+          defer_read_completed));
+  TestResourceHandler* test_handler = scoped_test_handler.get();
+  std::unique_ptr<MimeSniffingResourceHandler> mime_sniffing_handler(
+      new MimeSniffingResourceHandler(
+          std::move(scoped_test_handler), &host, &plugin_service,
+          intercepting_handler.get(), request.get()));
+
+  TestResourceController resource_controller;
+  mime_sniffing_handler->SetController(&resource_controller);
+
+  int expected_resume_calls = 0;
+
+  bool defer = false;
+  mime_sniffing_handler->OnWillStart(GURL(), &defer);
+
+  // The response should not be sniffed.
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+  response->head.mime_type.assign("text/html");
+
+  // Simulate the response starting. There should be no need for buffering, so
+  // the return value should be that of the next handler.
+  EXPECT_EQ(response_started,
+            mime_sniffing_handler->OnResponseStarted(response.get(), &defer));
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+  if (!response_started) {
+    EXPECT_FALSE(defer);
+
+    EXPECT_EQ(1, test_handler->on_will_start_called());
+    EXPECT_EQ(0, test_handler->on_request_redirected_called());
+    EXPECT_EQ(1, test_handler->on_response_started_called());
+    EXPECT_EQ(0, test_handler->on_will_read_called());
+    EXPECT_EQ(0, test_handler->on_read_completed_called());
+
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  EXPECT_EQ(defer_response_started, defer);
+  if (defer) {
+    EXPECT_EQ(MimeSniffingResourceHandler::STATE_REPLAYING_RESPONSE_RECEIVED,
+              mime_sniffing_handler->state_);
+    expected_resume_calls++;
+    mime_sniffing_handler->Resume();
+  }
+
+  EXPECT_EQ(expected_resume_calls, resource_controller.resume_call_count());
+
+  // The MimeSniffingResourceHandler should be acting as a pass-through
+  // ResourceHandler.
+  scoped_refptr<net::IOBuffer> read_buffer;
+  int buf_size = 0;
+  EXPECT_EQ(will_read,
+            mime_sniffing_handler->OnWillRead(&read_buffer, &buf_size, -1));
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+  if (!will_read) {
+    EXPECT_EQ(1, test_handler->on_will_start_called());
+    EXPECT_EQ(0, test_handler->on_request_redirected_called());
+    EXPECT_EQ(1, test_handler->on_response_started_called());
+    EXPECT_EQ(1, test_handler->on_will_read_called());
+    EXPECT_EQ(0, test_handler->on_read_completed_called());
+
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  defer = false;
+  EXPECT_EQ(read_completed,
+            mime_sniffing_handler->OnReadCompleted(2000, &defer));
+  EXPECT_EQ(0, resource_controller.cancel_call_count());
+
+  EXPECT_EQ(1, test_handler->on_will_start_called());
+  EXPECT_EQ(0, test_handler->on_request_redirected_called());
+  EXPECT_EQ(1, test_handler->on_response_started_called());
+  EXPECT_EQ(1, test_handler->on_will_read_called());
+  EXPECT_EQ(1, test_handler->on_read_completed_called());
+
+  if (!read_completed) {
+    EXPECT_FALSE(defer);
+
+    // Process all messages to ensure proper test teardown.
+    content::RunAllPendingInMessageLoop();
+    return;
+  }
+
+  EXPECT_EQ(defer_read_completed, defer);
+  if (defer) {
+    expected_resume_calls++;
+    mime_sniffing_handler->Resume();
+  }
+  EXPECT_EQ(expected_resume_calls, resource_controller.resume_call_count());
+
+  // Process all messages to ensure proper test teardown.
+  content::RunAllPendingInMessageLoop();
+}
+
+// Test that the proper Accept: header is set based on the ResourceType
+TEST_F(MimeSniffingResourceHandlerTest, AcceptHeaders) {
+  EXPECT_EQ(
+      "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,"
+      "*/*;q=0.8",
+      TestAcceptHeaderSetting(RESOURCE_TYPE_MAIN_FRAME));
+  EXPECT_EQ(
+      "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,"
+      "*/*;q=0.8",
+      TestAcceptHeaderSetting(RESOURCE_TYPE_SUB_FRAME));
+  EXPECT_EQ("text/css,*/*;q=0.1",
+            TestAcceptHeaderSetting(RESOURCE_TYPE_STYLESHEET));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_SCRIPT));
+  EXPECT_EQ("image/webp,image/*,*/*;q=0.8",
+            TestAcceptHeaderSetting(RESOURCE_TYPE_IMAGE));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_FONT_RESOURCE));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_SUB_RESOURCE));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_OBJECT));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_MEDIA));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_WORKER));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_SHARED_WORKER));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_PREFETCH));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_FAVICON));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_XHR));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_PING));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_SERVICE_WORKER));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_CSP_REPORT));
+  EXPECT_EQ("*/*", TestAcceptHeaderSetting(RESOURCE_TYPE_PLUGIN_RESOURCE));
+
+  // Ensure that if an Accept header is already set, it is not overwritten.
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  request->SetExtraRequestHeaderByName("Accept", "*", true);
+  EXPECT_EQ("*", TestAcceptHeaderSettingWithURLRequest(RESOURCE_TYPE_XHR,
+                                                       request.get()));
+}
+
+// Test that stream requests are correctly intercepted under the right
+// circumstances. Test is not relevent when plugins are disabled.
+#if defined(ENABLE_PLUGINS)
+TEST_F(MimeSniffingResourceHandlerTest, StreamHandling) {
+  bool allow_download;
+  bool must_download;
+  ResourceType resource_type;
+
+  // Ensure the stream is handled by MaybeInterceptAsStream in the
+  // ResourceDispatcherHost.
+  set_stream_has_handler(true);
+  set_plugin_available(true);
+
+  // Main frame request with no download allowed. Stream shouldn't be
+  // intercepted.
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_MAIN_FRAME;
+  EXPECT_FALSE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Main frame request with download allowed. Stream should be intercepted.
+  allow_download = true;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_MAIN_FRAME;
+  EXPECT_TRUE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Main frame request with download forced. Stream shouldn't be intercepted.
+  allow_download = true;
+  must_download = true;
+  resource_type = RESOURCE_TYPE_MAIN_FRAME;
+  EXPECT_FALSE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Sub-resource request with download not allowed. Stream shouldn't be
+  // intercepted.
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_SUB_RESOURCE;
+  EXPECT_FALSE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Plugin resource request with download not allowed. Stream shouldn't be
+  // intercepted.
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_PLUGIN_RESOURCE;
+  EXPECT_FALSE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Object request with download not allowed. Stream should be intercepted.
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_OBJECT;
+  EXPECT_TRUE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Test the cases where the stream isn't handled by MaybeInterceptAsStream
+  // in the ResourceDispatcherHost.
+  set_stream_has_handler(false);
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_OBJECT;
+  EXPECT_FALSE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Test the cases where the stream handled by MaybeInterceptAsStream
+  // with plugin not available. This is the case when intercepting streams for
+  // the streamsPrivate extensions API.
+  set_stream_has_handler(true);
+  set_plugin_available(false);
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_OBJECT;
+  EXPECT_TRUE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+
+  // Test the cases where the stream handled by MaybeInterceptAsStream
+  // with plugin not available. This is the case when intercepting streams for
+  // the streamsPrivate extensions API with stale plugin.
+  set_plugin_stale(true);
+  allow_download = false;
+  must_download = false;
+  resource_type = RESOURCE_TYPE_OBJECT;
+  EXPECT_TRUE(
+      TestStreamIsIntercepted(allow_download, must_download, resource_type));
+}
+#endif
+
+// Test that the MimeSniffingHandler operates properly when it doesn't sniff
+// resources.
+TEST_F(MimeSniffingResourceHandlerTest, NoSniffing) {
+  // Test simple case.
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  // Test deferral in OnResponseStarted and/or in OnReadCompleted.
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      true  /* defer_read_completed */);
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      true  /* defer_read_completed */);
+
+  // Test cancel in OnResponseStarted, OnWillRead, OnReadCompleted.
+  TestHandlerNoSniffing(
+      false /* response_started_succeeds */,
+      false /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  // Test cancel after OnResponseStarted deferral.
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerNoSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  content::RunAllPendingInMessageLoop();
+}
+
+// Test that the MimeSniffingHandler operates properly when it sniffs
+// resources.
+TEST_F(MimeSniffingResourceHandlerTest, Sniffing) {
+  // Test simple case.
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  // Test deferral in OnResponseStarted and/or in OnReadCompleted.
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      true  /* defer_read_completed */);
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      true  /* read_completed_succeeds */,
+      true  /* defer_read_completed */);
+
+  // Test cancel in OnResponseStarted, OnWillRead, OnReadCompleted.
+  TestHandlerSniffing(
+      false /* response_started_succeeds */,
+      false /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      false /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  // Test cancel after OnResponseStarted deferral.
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      false /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+  TestHandlerSniffing(
+      true  /* response_started_succeeds */,
+      true  /* defer_response_started */,
+      true  /* will_read_succeeds */,
+      false /* read_completed_succeeds */,
+      false /* defer_read_completed */);
+
+  content::RunAllPendingInMessageLoop();
+}
+
+// Tests that 304s do not trigger a change in handlers.
+TEST_F(MimeSniffingResourceHandlerTest, 304Handling) {
+  net::URLRequestContext context;
+  std::unique_ptr<net::URLRequest> request(context.CreateRequest(
+      GURL("http://www.google.com"), net::DEFAULT_PRIORITY, nullptr));
+  ResourceRequestInfo::AllocateForTesting(request.get(),
+                                          RESOURCE_TYPE_MAIN_FRAME,
+                                          nullptr,  // context
+                                          0,        // render_process_id
+                                          0,        // render_view_id
+                                          0,        // render_frame_id
+                                          true,     // is_main_frame
+                                          false,    // parent_is_main_frame
+                                          true,     // allow_download
+                                          true,     // is_async
+                                          false);   // is_using_lofi
+
+  TestResourceDispatcherHost host(false);
+  TestResourceDispatcherHostDelegate host_delegate(false);
+  host.SetDelegate(&host_delegate);
+
+  TestFakePluginService plugin_service(false, false);
+  std::unique_ptr<ResourceHandler> intercepting_handler(
+      new InterceptingResourceHandler(std::unique_ptr<ResourceHandler>(),
+                                      nullptr));
+  std::unique_ptr<ResourceHandler> mime_handler(new MimeSniffingResourceHandler(
+      std::unique_ptr<ResourceHandler>(
+          new TestResourceHandler(true, false, true, true, false)),
+      &host, &plugin_service,
+      static_cast<InterceptingResourceHandler*>(intercepting_handler.get()),
+      request.get()));
+
+  TestResourceController resource_controller;
+  mime_handler->SetController(&resource_controller);
+
+  // Simulate a 304 response.
+  scoped_refptr<ResourceResponse> response(new ResourceResponse);
+  // The MIME type isn't important but it shouldn't be empty.
+  response->head.mime_type = "application/pdf";
+  response->head.headers = new net::HttpResponseHeaders("HTTP/1.x 304 OK");
+
+  // The response is received. No new ResourceHandler should be created to
+  // handle the download.
+  bool defer = false;
+  mime_handler->OnResponseStarted(response.get(), &defer);
+  EXPECT_FALSE(defer);
+  EXPECT_FALSE(host.new_resource_handler());
+
+  content::RunAllPendingInMessageLoop();
+}
+
+}  // namespace content