Make OSMesa GL implementation advertise supported functionality as ES2 extensions

ui/gfx/gl/gl_implementation.h

Index: ui/gfx/gl/gl_implementation.h
===================================================================
--- ui/gfx/gl/gl_implementation.h	(revision 102100)
+++ ui/gfx/gl/gl_implementation.h	(working copy)
@@ -42,6 +42,10 @@
 // Get the current GL implementation.
 GL_EXPORT GLImplementation GetGLImplementation();
 
+// Does the underlying GL support all features from Desktop GL 2.0 that were
+// removed from the ES 2.0 spec without requiring specific extension strings.
+GL_EXPORT bool HasDesktopGLFeatures();
+
 // Get the GL implementation with a given name.
 GLImplementation GetNamedGLImplementation(const std::wstring& name);