Plumb thru that we cache the front buffer.

third_party/khronos/GLES2/gl2ext.h

 #ifndef __gl2ext_h_
 #define __gl2ext_h_
 
 /* $Revision: 15049 $ on $Date:: 2011-07-06 17:28:16 -0700 #$ */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /*
@@ skipping 1348 matching lines @@
 #ifdef GL_GLEXT_PROTOTYPES
 #define glPostSubBufferCHROMIUM GLES2_GET_FUN(PostSubBufferCHROMIUM)
 #if !defined(GLES2_USE_CPP_BINDINGS)
 GL_APICALL void GL_APIENTRY glPostSubBufferCHROMIUM (GLint x, GLint y, GLint width, GLint height);
 #endif
 #else
 typedef void (GL_APIENTRYP PFNGLPOSTSUBBUFFERCHROMIUM) (GLint x, GLint y, GLint width, GLint height);
 #endif
 #endif
 
+/* GL_CHROMIUM_front_buffer_cached */
+/* This extension implies that there is a cache of the front buffer of the
+ * surface supporting this extension (e.g. on OSX the front buffer
+ * is often backed by an IOSurface). Hence we do not need to redraw
+ * (via a SwapBuffers) in order to display the last frame.
+ */
+#ifndef GL_CHROMIUM_front_buffer_cached
+#define GL_CHROMIUM_front_buffer_cached 1
+#endif
+
 /* GL_ARB_robustness */
 /* This extension is subsetted for the moment, incorporating only the
  * enums necessary to describe the reasons that we might encounter for
  * losing the context. The entry point querying the reset status is
  * not yet incorporated; to do so, a spec will be needed of a GLES2
  * subset of GL_ARB_robustness.
  */
 #ifndef GL_ARB_robustness
 #define GL_ARB_robustness 1
 #ifndef GL_GUILTY_CONTEXT_RESET_ARB
@@ skipping 55 matching lines @@
 #else
 typedef void (GL_APIENTRYP PFNGLTEXIMAGEIOSURFACE2DCHROMIUM) (GLenum target, GLsizei width, GLsizei height, GLuint ioSurfaceId, GLuint plane);
 #endif
 #endif
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* __gl2ext_h_ */