gpu: don't try to discard/recreate backbuffer while draws are deferred.

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 646c5b18fd1832f8329167a517bc57e6e1a151df..b9299627125beaf5317c4ce9844ea4bea436cb18 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -714,14 +714,24 @@ void GpuCommandBufferStub::OnDiscardBackbuffer() {
   TRACE_EVENT0("gpu", "GpuCommandBufferStub::OnDiscardBackbuffer");
   if (!surface_)
     return;
-  surface_->SetBackbufferAllocation(false);
+  if (surface_->DeferDraws()) {
+    DCHECK(!IsScheduled());
+    channel_->RequeueMessage();
+  } else {
+    surface_->SetBackbufferAllocation(false);
+  }
 }
 
 void GpuCommandBufferStub::OnEnsureBackbuffer() {
   TRACE_EVENT0("gpu", "GpuCommandBufferStub::OnEnsureBackbuffer");
   if (!surface_)
     return;
-  surface_->SetBackbufferAllocation(true);
+  if (surface_->DeferDraws()) {
+    DCHECK(!IsScheduled());
+    channel_->RequeueMessage();
+  } else {
+    surface_->SetBackbufferAllocation(true);
+  }
 }
 
 void GpuCommandBufferStub::AddSyncPoint(uint32 sync_point) {