Allow GLSurface to indicate that it supports a specific extension.

ui/gfx/gl/gl_surface.cc

Index: ui/gfx/gl/gl_surface.cc
diff --git a/ui/gfx/gl/gl_surface.cc b/ui/gfx/gl/gl_surface.cc
index 1064878d5300f53b02851114706b182690936145..9276d00d6d061a814d64ac3dd5b749e1d9cab7c6 100644
--- a/ui/gfx/gl/gl_surface.cc
+++ b/ui/gfx/gl/gl_surface.cc
@@ -90,12 +90,13 @@ bool GLSurface::Resize(const gfx::Size& size) {
   return false;
 }
 
-unsigned int GLSurface::GetBackingFrameBufferObject() {
-  return 0;
+std::string GLSurface::GetExtensions() {
+  DCHECK_EQ(GetCurrent(), this);
+  return std::string("");
 }
 
-bool GLSurface::SupportsPostSubBuffer() {
-  return false;
+unsigned int GLSurface::GetBackingFrameBufferObject() {
+  return 0;
 }
 
 bool GLSurface::PostSubBuffer(int x, int y, int width, int height) {