Fix TexImage2D clearing too agressively

gpu/command_buffer/service/gles2_cmd_decoder.h

 // Copyright (c) 2012 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 GLES2Decoder class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_
 
 #include <vector>
@@ skipping 127 matching lines @@
       int level,
       unsigned format,
       unsigned type,
       int width,
       int height,
       bool is_texture_immutable) = 0;
 
   // A callback for messages from the decoder.
   virtual void SetMsgCallback(const MsgCallback& callback) = 0;
 
+  static bool IsAngle();
+
+  // Used for testing only
+  static void set_testing_force_is_angle(bool force);
+
  protected:
   GLES2Decoder();
 
  private:
   bool debug_;
   bool log_commands_;
+  static bool testing_force_is_angle_;
 
   DISALLOW_COPY_AND_ASSIGN(GLES2Decoder);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_