Use blocking worker pool for sync file operations in Pepper.

content/browser/renderer_host/pepper/pepper_file_message_filter.h

Index: content/browser/renderer_host/pepper/pepper_file_message_filter.h
diff --git a/content/browser/renderer_host/pepper/pepper_file_message_filter.h b/content/browser/renderer_host/pepper/pepper_file_message_filter.h
index c5065f16e35fc24a7f564423b6cc8befbcdbf087..34a94ffb368047b6380946f1ae105524b317d3f2 100644
--- a/content/browser/renderer_host/pepper/pepper_file_message_filter.h
+++ b/content/browser/renderer_host/pepper/pepper_file_message_filter.h
@@ -33,9 +33,8 @@ class PepperFileMessageFilter : public content::BrowserMessageFilter {
   explicit PepperFileMessageFilter(int child_id);
 
   // content::BrowserMessageFilter methods:
-  virtual void OverrideThreadForMessage(
-      const IPC::Message& message,
-      content::BrowserThread::ID* thread) OVERRIDE;
+  virtual base::TaskRunner* OverrideTaskRunnerForMessage(
+      const IPC::Message& message) OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
                                  bool* message_was_ok) OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;