Add MGL entry points and port spinning_cube to use them

mojo/public/c/gpu/GLES2/gl2.h

 #ifndef __gl2_h_
 #define __gl2_h_ 1
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /*
 ** Copyright (c) 2013-2014 The Khronos Group Inc.
 **
@@ skipping 18 matching lines @@
 */
 /*
 ** This header is generated from the Khronos OpenGL / OpenGL ES XML
 ** API Registry. The current version of the Registry, generator scripts
 ** used to make the header, and the header can be found at
 **   http://www.opengl.org/registry/
 **
 ** Khronos $Revision: 28366 $ on $Date: 2014-10-20 11:29:02 +0200 (Mon, 20 Oct 2014) $
 */
 
-#include <GLES2/gl2chromium.h>
+#include <GLES2/gl2mojo.h>
 #include <GLES2/gl2platform.h>
 
 /* Generated on date 20141020 */
 
 /* Generated C header for:
  * API: gles2
  * Profile: common
  * Versions considered: 2\.[0-9]
  * Versions emitted: .*
  * Default extensions included: None
@@ skipping 467 matching lines @@
 GL_APICALL void GL_APIENTRY glVertexAttrib4fv (GLuint index, const GLfloat *v);
 GL_APICALL void GL_APIENTRY glVertexAttribPointer (GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void *pointer);
 GL_APICALL void GL_APIENTRY glViewport (GLint x, GLint y, GLsizei width, GLsizei height);
 #endif /* GL_ES_VERSION_2_0 */
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif