Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 26c80f20f131a7315bd8ab6d504ab44329779c1f..a51f4b157316c73175abc645df5c5e44b44ac93a 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -589,6 +589,10 @@ class GLES2DecoderImpl : public base::SupportsWeakPtr<GLES2DecoderImpl>,
       const base::Callback<void(gfx::Size)>& callback);
 
   virtual void SetMsgCallback(const MsgCallback& callback);
+  virtual void SetDiscardBackbufferCallback(
+      const DiscardBackbufferCallback& callback);
+  virtual void SetEnsureBackbufferCallback(
+      const EnsureBackbufferCallback& callback);
 
   virtual void SetStreamTextureManager(StreamTextureManager* manager);
   virtual bool GetServiceTextureId(uint32 client_texture_id,
@@ -1525,6 +1529,8 @@ class GLES2DecoderImpl : public base::SupportsWeakPtr<GLES2DecoderImpl>,
   base::Callback<void(gfx::Size)> resize_callback_;
 
   MsgCallback msg_callback_;
+  DiscardBackbufferCallback discard_backbuffer_callback_;
+  EnsureBackbufferCallback ensure_backbuffer_callback_;
 
   StreamTextureManager* stream_texture_manager_;
 
@@ -2754,6 +2760,16 @@ void GLES2DecoderImpl::SetMsgCallback(const MsgCallback& callback) {
   msg_callback_ = callback;
 }
 
+void GLES2DecoderImpl::SetDiscardBackbufferCallback(
+    const DiscardBackbufferCallback& callback) {
+  discard_backbuffer_callback_ = callback;
+}
+
+void GLES2DecoderImpl::SetEnsureBackbufferCallback(
+    const EnsureBackbufferCallback& callback) {
+  ensure_backbuffer_callback_ = callback;
+}
+
 void GLES2DecoderImpl::SetStreamTextureManager(StreamTextureManager* manager) {
   stream_texture_manager_ = manager;
 }
@@ -8410,6 +8426,22 @@ void GLES2DecoderImpl::DoTexStorage2DEXT(
   }
 }
 
+error::Error GLES2DecoderImpl::HandleDiscardBackbufferCHROMIUM(
+    uint32 immediate_data_size, const gles2::DiscardBackbufferCHROMIUM& c) {
+  TRACE_EVENT0("gpu", "glDiscardBackbuffer");
+  if (!discard_backbuffer_callback_.is_null())
+    discard_backbuffer_callback_.Run();
+  return error::kNoError;
+}
+
+error::Error GLES2DecoderImpl::HandleEnsureBackbufferCHROMIUM(
+    uint32 immediate_data_size, const gles2::EnsureBackbufferCHROMIUM& c) {
+  TRACE_EVENT0("gpu", "glEnsureBackbuffer");
+  if (!ensure_backbuffer_callback_.is_null())
+    ensure_backbuffer_callback_.Run();
+  return error::kNoError;
+}
+
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.