Add MGL entry points and port spinning_cube to use them

mojo/public/c/gpu/GLES2/gl2mojo_autogen.h

 // Copyright 2014 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 is auto-generated from
 // gpu/command_buffer/build_gles2_cmd_buffer.py
 // It's formatted by clang-format using chromium coding style:
 //    clang-format -i -style=chromium filename
 // DO NOT EDIT!
 
-// This file contains Chromium-specific GLES2 declarations.
+// This file contains Mojo-specific GLES2 declarations.
 
-#ifndef GPU_GLES2_GL2CHROMIUM_AUTOGEN_H_
-#define GPU_GLES2_GL2CHROMIUM_AUTOGEN_H_
+#ifndef GPU_GLES2_GL2MOJO_AUTOGEN_H_
+#define GPU_GLES2_GL2MOJO_AUTOGEN_H_
 
 #define glActiveTexture GLES2_GET_FUN(ActiveTexture)
 #define glAttachShader GLES2_GET_FUN(AttachShader)
 #define glBindAttribLocation GLES2_GET_FUN(BindAttribLocation)
 #define glBindBuffer GLES2_GET_FUN(BindBuffer)
 #define glBindBufferBase GLES2_GET_FUN(BindBufferBase)
 #define glBindBufferRange GLES2_GET_FUN(BindBufferRange)
 #define glBindFramebuffer GLES2_GET_FUN(BindFramebuffer)
 #define glBindRenderbuffer GLES2_GET_FUN(BindRenderbuffer)
 #define glBindSampler GLES2_GET_FUN(BindSampler)
@@ skipping 295 matching lines @@
 #define glWaitSyncPointCHROMIUM GLES2_GET_FUN(WaitSyncPointCHROMIUM)
 #define glDrawBuffersEXT GLES2_GET_FUN(DrawBuffersEXT)
 #define glDiscardBackbufferCHROMIUM GLES2_GET_FUN(DiscardBackbufferCHROMIUM)
 #define glScheduleOverlayPlaneCHROMIUM \
   GLES2_GET_FUN(ScheduleOverlayPlaneCHROMIUM)
 #define glSwapInterval GLES2_GET_FUN(SwapInterval)
 #define glMatrixLoadfCHROMIUM GLES2_GET_FUN(MatrixLoadfCHROMIUM)
 #define glMatrixLoadIdentityCHROMIUM GLES2_GET_FUN(MatrixLoadIdentityCHROMIUM)
 #define glBlendBarrierKHR GLES2_GET_FUN(BlendBarrierKHR)
 
-#endif  // GPU_GLES2_GL2CHROMIUM_AUTOGEN_H_
+#endif  // GPU_GLES2_GL2MOJO_AUTOGEN_H_