GPU: Only allow the UI channel to preempt if all stubs are scheduled.

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index 550c17433f05f26415d07ccc53718e2c66d05563..2c9da0ce0989bd7d30afea931e70bd0523943c19 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -270,6 +270,7 @@ void GpuCommandBufferStub::OnReschedule() {
     return;
 
   channel_->OnScheduled();
+  channel_->StubSchedulingChanged();
 }
 
 bool GpuCommandBufferStub::MakeCurrent() {
@@ -487,6 +488,9 @@ void GpuCommandBufferStub::OnInitialize(
       base::Bind(&GpuCommandBufferStub::OnParseError, base::Unretained(this)));
   scheduler_->SetScheduledCallback(
       base::Bind(&GpuCommandBufferStub::OnReschedule, base::Unretained(this)));
+  scheduler_->SetDescheduledCallback(
+      base::Bind(&GpuChannel::StubSchedulingChanged,
+                 base::Unretained(channel_)));

[piman, 2013/02/27 21:54:43]

Could we merge the 2 callbacks (eg passing the scheduled flag, or having the
callback check IsScheduled() )?
It's easier to follow if both paths get routed to the same class, and it avoids
the explosion of callbacks.

[jonathan.backer, 2013/02/28 21:43:56]

Done.

 
   if (watchdog_) {
     scheduler_->SetCommandProcessedCallback(