Fix blits from multisampled renderbuffers to alpha:false WebGL back buffer.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.h

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains the GLES2DecoderPassthroughImpl class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_
 
 #include "base/memory/ref_counted.h"
@@ skipping 285 matching lines @@
   void InsertError(GLenum error, const std::string& message);
   GLenum PopError();
   bool FlushErrors();
 
   bool IsEmulatedQueryTarget(GLenum target) const;
   error::Error ProcessQueries(bool did_finish);
   void RemovePendingQuery(GLuint service_id);
 
   void UpdateTextureBinding(GLenum target, GLuint client_id, GLuint service_id);
 
+  error::Error BindTexImage2DCHROMIUMImpl(GLenum target,
+                                          GLenum internalformat,
+                                          GLint image_id);
+
   int commands_to_process_;
 
   DebugMarkerManager debug_marker_manager_;
   Logger logger_;
 
 #define GLES2_CMD_OP(name) \
   Error Handle##name(uint32_t immediate_data_size, const volatile void* data);
 
   GLES2_COMMAND_LIST(GLES2_CMD_OP)
 #undef GLES2_CMD_OP
@@ skipping 85 matching lines @@
 
 // Include the prototypes of all the doer functions from a separate header to
 // keep this file clean.
 #include "gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doer_prototypes.h"
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_PASSTHROUGH_H_