Support dynamic switching between integrated and discrete GPUs on Mac OS X.

ui/gfx/gl/gl_share_group.cc

Index: ui/gfx/gl/gl_share_group.cc
===================================================================
--- ui/gfx/gl/gl_share_group.cc	(revision 105158)
+++ ui/gfx/gl/gl_share_group.cc	(working copy)
@@ -20,11 +20,19 @@
 }
 
 void* GLShareGroup::GetHandle() {
+  GLContext* context = GetContext();
+  if (context)
+    return context->GetHandle();
+
+  return NULL;
+}
+
+GLContext* GLShareGroup::GetContext() {
   for (ContextSet::iterator it = contexts_.begin();
        it != contexts_.end();
        ++it) {
-     if ((*it)->GetHandle())
-       return (*it)->GetHandle();
+    if ((*it)->GetHandle())
+      return *it;
   }
 
   return NULL;