Added a way for sync point clients to issue out of order waits.

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 8aabdca64837872060e04791d90e814e63f2cd0a..e30f81f735cf73773e79d5c77ed27fd2c159551d 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -1009,9 +1009,11 @@ void GpuCommandBufferStub::OnSignalSyncToken(const gpu::SyncToken& sync_token,
           sync_token.namespace_id(), sync_token.command_buffer_id());
 
   if (release_state) {
-    sync_point_client_->Wait(release_state.get(), sync_token.release_count(),
-                             base::Bind(&GpuCommandBufferStub::OnSignalAck,
-                                        this->AsWeakPtr(), id));
+    // This wait must use the out of order variant since it is not processed
+    // within the global order.

[piman, 2016/01/07 01:16:22]

I don't think that's true, this is processed on the main thread, just like every
other message (it would be a good idea to do on the IO thread, actually, but we
don't do that now).

[David Yen, 2016/01/07 18:40:58]

You are right, this should be Wait instead of WaitOutOfOrder. I forgot that the
command buffer stub runs on the main thread and has an order number attached to
every command. That is not true for the InProcess case though.

Alternatively we can do this on the IO thread using WaitOutOfOrder if we want
to. I will change it back for now though.

+    sync_point_client_->WaitOutOfOrder(
+        release_state.get(), sync_token.release_count(),
+        base::Bind(&GpuCommandBufferStub::OnSignalAck, this->AsWeakPtr(), id));
   } else {
     OnSignalAck(id);
   }