Inject timestamps to resource messages.

content/renderer/devtools/devtools_agent_filter.h

Index: content/renderer/devtools/devtools_agent_filter.h
diff --git a/content/renderer/devtools/devtools_agent_filter.h b/content/renderer/devtools/devtools_agent_filter.h
index e7f78613807bcccb8f50885661dbf2a1e8acf3b9..1b99fcdba27fd7f99a5f23ae04c545dbd07f35eb 100644
--- a/content/renderer/devtools/devtools_agent_filter.h
+++ b/content/renderer/devtools/devtools_agent_filter.h
@@ -16,6 +16,7 @@ class MessageLoop;
 }
 
 namespace content {
+class ResourceDispatcher;
 
 // DevToolsAgentFilter is registered as an IPC filter in order to be able to
 // dispatch messages while on the IO thread. The reason for that is that while
@@ -23,10 +24,15 @@ namespace content {
 // are being dispatched there. While holding the thread in a tight loop,
 // v8 provides thread-safe Api for controlling debugger. In our case v8's Api
 // is being used from this communication agent on the IO thread.
+//
+// Another reason is that ResourceDispatcher needs child process timestamps
+// not affected by long rendering / JS tasks. When specific resource message is
+// processed "ResourceDispatcher::set_io_timestamp" task with bound timestamp
+// is posted to main thread. It is served just before resource message.

[Charlie Reis, 2013/05/24 16:17:08]

Again, this seems unrelated to DevTools.  I could imagine DevTools becoming a
component that isn't always guaranteed to be present, in which case you'd
accidentally lose this logic.

I don't know what the overhead of adding a new MessageFilter is, though, so I'll
defer to Darin.

[eustas, 2013/05/27 12:03:57]

Done.

 class DevToolsAgentFilter : public IPC::ChannelProxy::MessageFilter {
  public:
   // There is a single instance of this class instantiated by the RenderThread.
-  DevToolsAgentFilter();
+  explicit DevToolsAgentFilter(ResourceDispatcher* resource_dispatcher);
 
   static void SendRpcMessage(const DevToolsMessageData& data);
 
@@ -39,6 +45,7 @@ class DevToolsAgentFilter : public IPC::ChannelProxy::MessageFilter {
  private:
   void OnDispatchOnInspectorBackend(const std::string& message);
 
+  ResourceDispatcher* resource_dispatcher_;
   bool message_handled_;
   base::MessageLoop* render_thread_loop_;
   int current_routing_id_;