Add ChildMessageFilter, a base class for renderer/worker cross-thread MessageFilter

content/child/indexed_db/indexed_db_message_filter.cc

Index: content/child/indexed_db/indexed_db_message_filter.cc
diff --git a/content/child/indexed_db/indexed_db_message_filter.cc b/content/child/indexed_db/indexed_db_message_filter.cc
index 7022925e6d0569898bc5a13fe3a13c72456b90ce..2d0a341af233f15e308b26cb75827b4e06bf1fdf 100644
--- a/content/child/indexed_db/indexed_db_message_filter.cc
+++ b/content/child/indexed_db/indexed_db_message_filter.cc
@@ -4,50 +4,32 @@
 
 #include "content/child/indexed_db/indexed_db_message_filter.h"
 
-#include "base/bind.h"
-#include "base/location.h"
-#include "base/message_loop/message_loop_proxy.h"
-#include "base/pickle.h"
 #include "content/child/indexed_db/indexed_db_dispatcher.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/common/indexed_db/indexed_db_messages.h"
-#include "webkit/child/worker_task_runner.h"
-
-using webkit_glue::WorkerTaskRunner;
 
 namespace content {
 
 IndexedDBMessageFilter::IndexedDBMessageFilter(
     ThreadSafeSender* thread_safe_sender)
-    : main_thread_loop_proxy_(base::MessageLoopProxy::current()),
-      thread_safe_sender_(thread_safe_sender) {
+    : thread_safe_sender_(thread_safe_sender) {
 }
 
-bool IndexedDBMessageFilter::OnMessageReceived(const IPC::Message& msg) {
+IndexedDBMessageFilter::~IndexedDBMessageFilter() {}
+
+bool IndexedDBMessageFilter::OverrideThreadIDForMessage(
+    const IPC::Message& msg, int* ipc_thread_id) {
   if (IPC_MESSAGE_CLASS(msg) != IndexedDBMsgStart)
     return false;
-  int ipc_thread_id = -1;
-  bool result = PickleIterator(msg).ReadInt(&ipc_thread_id);
-  DCHECK(result);
-  base::Closure closure = base::Bind(
-      &IndexedDBMessageFilter::DispatchMessage, this, msg);
-  if (!ipc_thread_id) {
-    main_thread_loop_proxy_->PostTask(FROM_HERE, closure);
-    return true;
-  }
-  if (WorkerTaskRunner::Instance()->PostTask(ipc_thread_id, closure))
-    return true;
-
-  // Message for a terminated worker - perform necessary cleanup
-  OnStaleMessageReceived(msg);
-  return true;
+  return PickleIterator(msg).ReadInt(ipc_thread_id);
 }
 
-IndexedDBMessageFilter::~IndexedDBMessageFilter() {}
-
-void IndexedDBMessageFilter::DispatchMessage(const IPC::Message& msg) {
+bool IndexedDBMessageFilter::OnMessageReceived(const IPC::Message& msg) {
+  if (IPC_MESSAGE_CLASS(msg) != IndexedDBMsgStart)
+    return false;
   IndexedDBDispatcher::ThreadSpecificInstance(thread_safe_sender_.get())
       ->OnMessageReceived(msg);
+  return true;
 }
 
 void IndexedDBMessageFilter::OnStaleMessageReceived(const IPC::Message& msg) {