Add a file thread to the renderer process.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/3151029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@56917 0039d316-1c4b-4281-b951-d872f2087c98

chrome/renderer/render_thread.cc

@@ -307,6 +307,10 @@ RenderThread::~RenderThread() {
   db_message_filter_ = NULL;
   RemoveFilter(devtools_agent_filter_.get());
 
+  // Shutdown the file thread if it's running.
+  if (file_thread_.get())
+    file_thread_->Stop();
+
   if (webkit_client_.get())
     WebKit::shutdown();
 
@@ -1100,3 +1104,13 @@ std::string RenderThread::GetExtensionIdByBrowseExtent(const GURL& url) {
 
   return std::string();
 }
+
+scoped_refptr<base::MessageLoopProxy>
+RenderThread::GetFileThreadMessageLoopProxy() {
+  DCHECK(message_loop() == MessageLoop::current());
+  if (!file_thread_.get()) {
+    file_thread_.reset(new base::Thread("Renderer::FILE"));
+    file_thread_->Start();
+  }
+  return file_thread_->message_loop_proxy();
+}

chrome/renderer/render_thread.h

@@ -46,6 +46,11 @@ struct ViewMsg_ExtensionExtentsUpdated_Params;
 struct ViewMsg_New_Params;
 struct WebPreferences;
 
+namespace base {
+class MessageLoopProxy;
+class Thread;
+}
+
 namespace IPC {
 struct ChannelHandle;
 }
@@ -227,6 +232,11 @@ class RenderThread : public RenderThreadBase,
 
   std::string GetExtensionIdByBrowseExtent(const GURL& url);
 
+  // Returns a MessageLoopProxy instance corresponding to the message loop
+  // of the thread on which file operations should be run. Must be called
+  // on the renderer's main thread.
+  scoped_refptr<base::MessageLoopProxy> GetFileThreadMessageLoopProxy();
+
  private:
   virtual void OnControlMessageReceived(const IPC::Message& msg);
 
@@ -365,6 +375,9 @@ class RenderThread : public RenderThreadBase,
   struct ExtensionInfo;
   std::vector<ExtensionInfo> extension_extents_;
 
+  // A lazily initiated thread on which file operations are run.
+  scoped_ptr<base::Thread> file_thread_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderThread);
 };