Make BrowserMessageFilter support dispatching messages on different threads.

chrome/browser/browser_message_filter.cc

 // Copyright (c) 2010 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.
 
-#include "chrome/browser/browser_io_message_filter.h"
+#include "chrome/browser/browser_message_filter.h"
 
 #include "base/logging.h"
+#include "base/process.h"
 #include "base/process_util.h"
 #include "chrome/browser/renderer_host/browser_render_process_host.h"
 
-BrowserIOMessageFilter::BrowserIOMessageFilter() : channel_(NULL) {
+BrowserMessageFilter::BrowserMessageFilter()
+    : channel_(NULL), peer_handle_(base::kNullProcessHandle) {
 }
 
-BrowserIOMessageFilter::~BrowserIOMessageFilter() {
+BrowserMessageFilter::~BrowserMessageFilter() {
 }
 
-void BrowserIOMessageFilter::OnFilterAdded(IPC::Channel* channel) {
+void BrowserMessageFilter::OnFilterAdded(IPC::Channel* channel) {
   channel_ = channel;
 }
 
-void BrowserIOMessageFilter::OnChannelClosing() {
+void BrowserMessageFilter::OnChannelClosing() {
   channel_ = NULL;
 }
 
-void BrowserIOMessageFilter::OnChannelConnected(int32 peer_pid) {
+void BrowserMessageFilter::OnChannelConnected(int32 peer_pid) {
   if (!base::OpenProcessHandle(peer_pid, &peer_handle_)) {
     NOTREACHED();
   }
 }
 
-bool BrowserIOMessageFilter::Send(IPC::Message* msg) {
+bool BrowserMessageFilter::Send(IPC::Message* message) {
+  if (message->is_sync()) {
+    // We don't support sending synchronous messages from the browser.  If we
+    // really needed it, we can make this class derive from SyncMessageFilter
+    // but it seems better to not allow sending synchronous messages from the
+    // browser, since it might allow a corrupt/malicious renderer to hang us.
+    NOTREACHED() << "Can't send sync message through BrowserMessageFilter!";
+    return false;
+  }
+
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO,
+        FROM_HERE,
+        NewRunnableMethod(this, &BrowserMessageFilter::Send, message));
+    return true;
+  }
+
   if (channel_)
-    return channel_->Send(msg);
+    return channel_->Send(message);
 
-  delete msg;
+  delete message;
   return false;
 }
 
-void BrowserIOMessageFilter::BadMessageReceived(uint32 msg_type) {
+BrowserThread::ID BrowserMessageFilter::HandleMessageOnThread(
+    const IPC::Message& message) {
+  return BrowserThread::IO;
+}
+
+bool BrowserMessageFilter::OnMessageReceived(const IPC::Message& message) {
+  BrowserThread::ID thread = HandleMessageOnThread(message);
+  if (thread == BrowserThread::IO)
+    return DispatchMessage(message);
+
+  BrowserThread::PostTask(
+      thread, FROM_HERE,
+      NewRunnableMethod(
+          this, &BrowserMessageFilter::DispatchMessage, message));

[darin (slow to review), 2010/12/06 05:14:58]

This has the side effect of generating a PostTask for each BrowserMessageFilter,
even though only 1 instance really cares about each particular message.  It
seems like HandleMessageOnThread should provide the caller with a way to say
that they are not interested in a message.

[jam, 2010/12/06 07:24:43]

Each message filter's HandleMessageOnThread should only reply with a non-IO
thread if it wants to handle that specific message, so this shouldn't happen.

+  return true;
+}
+
+bool BrowserMessageFilter::DispatchMessage(const IPC::Message& message) {
+  bool message_was_ok = true;
+  bool rv = OnMessageReceived(message, &message_was_ok);
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO) || rv) <<
+      "Must handle messages that were dispatched to another thread!";
+  if (!message_was_ok)
+    BadMessageReceived(message.type());
+
+  return rv;
+}
+
+void BrowserMessageFilter::BadMessageReceived(uint32 msg_type) {
   BrowserRenderProcessHost::BadMessageTerminateProcess(msg_type, peer_handle());
 }