Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index cf55bb1771ccadd6795c3fbfd6466d42270b48fc..bbabc9433924754b46206fa0b76f765b12468658 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -3259,5 +3259,18 @@ void GLES2Implementation::DrawElementsInstancedANGLE(
 #endif
 }
 
+void GLES2Implementation::DiscardBackbufferCHROMIUM() {
+  GPU_CLIENT_SINGLE_THREAD_CHECK();
+  GPU_CLIENT_LOG("[" << this << "] glDiscardBackbufferCHROMIUM()");
+  helper_->DiscardBackbufferCHROMIUM();
+  helper_->CommandBufferHelper::Flush();
+}
+
+void GLES2Implementation::EnsureBackbufferCHROMIUM() {
+  GPU_CLIENT_SINGLE_THREAD_CHECK();
+  GPU_CLIENT_LOG("[" << this << "] glEnsureBackbufferCHROMIUM()");
+  helper_->EnsureBackbufferCHROMIUM();
+}
+
 }  // namespace gles2
 }  // namespace gpu