Implement client side PBOs for glReadPixel

gpu/GLES2/gl2extchromium.h

Index: gpu/GLES2/gl2extchromium.h
diff --git a/gpu/GLES2/gl2extchromium.h b/gpu/GLES2/gl2extchromium.h
index b8dbc30f80a6f65ea3d37058ada2ba053094c1e8..e250769569d26a8e3edd67745ca6f78d04ec82dd 100644
--- a/gpu/GLES2/gl2extchromium.h
+++ b/gpu/GLES2/gl2extchromium.h
@@ -71,7 +71,8 @@ typedef void (GL_APIENTRYP PFNGLCONSUMETEXTURECHROMIUMPROC) (
 
 #ifndef GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM
 // TODO(reveman): Get official numbers for this constants.
-#define GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM 0x88EC
+#define GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM 0x78EC
+#define GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM 0x78ED
 
 #ifdef GL_GLEXT_PROTOTYPES
 GL_APICALL void* GL_APIENTRY glMapBufferCHROMIUM(GLuint target,GLenum access);
@@ -84,7 +85,8 @@ typedef GLboolean (GL_APIENTRY PFNGLUNMAPBUFFERCHROMIUM) (GLuint target);
 
 #ifndef GL_PIXEL_UNPACK_TRANSFER_BUFFER_BINDING_CHROMIUM
 // TODO(reveman): Get official numbers for this constants.
-#define GL_PIXEL_UNPACK_TRANSFER_BUFFER_BINDING_CHROMIUM 0x88EF
+#define GL_PIXEL_UNPACK_TRANSFER_BUFFER_BINDING_CHROMIUM 0x78EF
+#define GL_PIXEL_PACK_TRANSFER_BUFFER_BINDING_CHROMIUM 0x78EE
 #endif
 #endif  /* GL_CHROMIUM_pixel_transfer_buffer_object */
 
@@ -578,4 +580,3 @@ typedef void (GL_APIENTRYP PFNGLWAITSYNCPOINTCHROMIUMPROC) (GLuint sync_point);
 #endif
 
 #endif  // GPU_GLES2_GL2EXTCHROMIUM_H_
-