Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_v8.h

 // Copyright (c) 2011 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.
 
 #ifndef NET_PROXY_PROXY_RESOLVER_V8_H_
 #define NET_PROXY_PROXY_RESOLVER_V8_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "net/base/net_export.h"
 #include "net/proxy/proxy_resolver.h"
 
 namespace net {
 
-class ProxyResolverJSBindings;
-
 // Implementation of ProxyResolver that uses V8 to evaluate PAC scripts.
 //
 // ----------------------------------------------------------------------------
 // !!! Important note on threading model:
 // ----------------------------------------------------------------------------
 // There can be only one instance of V8 running at a time. To enforce this
 // constraint, ProxyResolverV8 holds a v8::Locker during execution. Therefore
 // it is OK to run multiple instances of ProxyResolverV8 on different threads,
 // since only one will be running inside V8 at a time.
 //
 // It is important that *ALL* instances of V8 in the process be using
 // v8::Locker. If not there can be race conditions between the non-locked V8
 // instances and the locked V8 instances used by ProxyResolverV8 (assuming they
 // run on different threads).
 //
 // This is the case with the V8 instance used by chromium's renderer -- it runs
 // on a different thread from ProxyResolver (renderer thread vs PAC thread),
 // and does not use locking since it expects to be alone.
 class NET_EXPORT_PRIVATE ProxyResolverV8 : public ProxyResolver {
  public:
-  // Constructs a ProxyResolverV8 with custom bindings. ProxyResolverV8 takes
-  // ownership of |custom_js_bindings| and deletes it when ProxyResolverV8
-  // is destroyed.
-  explicit ProxyResolverV8(ProxyResolverJSBindings* custom_js_bindings);
+  // Interface for the javascript bindings.
+  class NET_EXPORT_PRIVATE JSBindings {
+   public:
+    enum ResolveDnsOperation {
+      DNS_RESOLVE,
+      DNS_RESOLVE_EX,
+      MY_IP_ADDRESS,
+      MY_IP_ADDRESS_EX,
+      NUM_DNS_OPERATIONS,
+    };
+
+    JSBindings() {}
+
+    virtual ~JSBindings() {}
+
+    // Handler for "dnsResolve()", "dnsResolveEx()", "myIpAddress()",
+    // "myIpAddressEx()". Returns true on success and fills |*output| with the
+    // result.
+    virtual bool ResolveDns(const std::string& host,
+                            ResolveDnsOperation op,
+                            std::string* output) = 0;
+
+    // Handler for "alert(message)"
+    virtual void Alert(const string16& message) = 0;
+
+    // Handler for when an error is encountered. |line_number| may be -1
+    // if a line number is not applicable to this error.
+    virtual void OnError(int line_number, const string16& error) = 0;
+  };
+
+  // Constructs a ProxyResolverV8.
+  ProxyResolverV8();
 
   virtual ~ProxyResolverV8();
 
-  ProxyResolverJSBindings* js_bindings() const { return js_bindings_.get(); }
+  JSBindings* js_bindings() const { return js_bindings_; }
+  void set_js_bindings(JSBindings* js_bindings) { js_bindings_ = js_bindings; }
 
   // ProxyResolver implementation:
   virtual int GetProxyForURL(const GURL& url,
                              ProxyInfo* results,
                              const net::CompletionCallback& /*callback*/,
                              RequestHandle* /*request*/,
                              const BoundNetLog& net_log) OVERRIDE;
   virtual void CancelRequest(RequestHandle request) OVERRIDE;
   virtual LoadState GetLoadState(RequestHandle request) const OVERRIDE;
-  virtual LoadState GetLoadStateThreadSafe(
-      RequestHandle request) const OVERRIDE;
   virtual void CancelSetPacScript() OVERRIDE;
   virtual void PurgeMemory() OVERRIDE;
-  virtual void Shutdown() OVERRIDE;
   virtual int SetPacScript(
       const scoped_refptr<ProxyResolverScriptData>& script_data,
       const net::CompletionCallback& /*callback*/) OVERRIDE;
 
  private:
   // Context holds the Javascript state for the most recently loaded PAC
   // script. It corresponds with the data from the last call to
   // SetPacScript().
   class Context;
+
   scoped_ptr<Context> context_;
 
-  scoped_ptr<ProxyResolverJSBindings> js_bindings_;
+  JSBindings* js_bindings_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverV8);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_V8_H_