Created multi-process-friendly PowerMonitor interface.

content/common/gpu/gpu_channel.cc

Index: content/common/gpu/gpu_channel.cc
diff --git a/content/common/gpu/gpu_channel.cc b/content/common/gpu/gpu_channel.cc
index 0c5172cf45cf0a9c5586381dc8f7687b3ee10c03..32244e23b65c8ccecb602edd3e05a886ef754d18 100644
--- a/content/common/gpu/gpu_channel.cc
+++ b/content/common/gpu/gpu_channel.cc
@@ -15,6 +15,7 @@
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop_proxy.h"
+#include "base/power_monitor/power_monitor.h"
 #include "base/process_util.h"
 #include "base/rand_util.h"
 #include "base/strings/string_util.h"
@@ -22,6 +23,7 @@
 #include "content/common/gpu/gpu_channel_manager.h"
 #include "content/common/gpu/gpu_messages.h"
 #include "content/common/gpu/sync_point_manager.h"
+#include "content/common/power_monitor_message_filter.h"
 #include "content/public/common/content_switches.h"
 #include "crypto/hmac.h"
 #include "gpu/command_buffer/common/mailbox.h"
@@ -487,6 +489,11 @@ bool GpuChannel::Init(base::MessageLoopProxy* io_message_loop,
   io_message_loop_ = io_message_loop;
   channel_->AddFilter(filter_.get());
 
+  PowerMonitorBroadcastSource* power_monitor_source_ =
+      static_cast<PowerMonitorBroadcastSource*>(

[vandebo (ex-Chrome), 2013/06/26 21:40:33]

Is it easy to get at the original source instead of having to do this cast?

+      base::PowerMonitor::Get()->Source());
+  channel_->AddFilter(power_monitor_source_->MessageFilter());

[vandebo (ex-Chrome), 2013/06/26 21:40:33]

Is there ever a RemoveFilter call?  The concern is that it may be possible for
MessageFilter() to continue receiving messages after power_monitor_source has
been cleaned up/destroyed.

[Ken Russell (switch to Gerrit), 2013/06/27 13:08:23]

This setup doesn't look correct to me. You want to process control messages
coming from the browser process to the GPU process. As far as I can tell, the
recipient of the GPU-related control messages coming from the browser in
gpu_process_host.cc are handled in GpuChildThread::OnControlMessageReceived and
GpuChannelManager::OnMessageReceived. In fact, I don't see where those messages
would be re-dispatched to all of the GpuChannels that have been established
between renderer processes and the GPU process, and it looks to me like this
filter is being added only to those connections. Basically, I think that the
setup for receiving the power messages should be done in gpu_main.cc, after the
initialization of the GpuChildThread, and that you should add the MessageFilter
to the GpuChildThread's channel().

[bajones, 2013/07/01 20:21:58]

I don't see any examples of a filter being removed in the code base.

[bajones, 2013/07/01 20:21:58]

I've moved the addition of the message filter into gpu_main.cc as suggested,
which has the happy side effect of completely avoiding the nasty cast! 

+
   return true;
 }