Refactor GL bindings so there is no global GLApi or DriverGL.

ui/gl/init/gl_initializer_ozone.cc

Index: ui/gl/init/gl_initializer_ozone.cc
diff --git a/ui/gl/init/gl_initializer_ozone.cc b/ui/gl/init/gl_initializer_ozone.cc
index 213ef8ba7a8bb623f5ea4d4a6e29e7e5556b3b1d..d0b7234b66440f90db168fb5a818f9fa79549ca8 100644
--- a/ui/gl/init/gl_initializer_ozone.cc
+++ b/ui/gl/init/gl_initializer_ozone.cc
@@ -47,6 +47,7 @@ bool InitializeGLOneOffPlatform() {
       return true;
     case kGLImplementationOSMesaGL:
     case kGLImplementationMockGL:
+    case kGLImplementationStubGL:
       return true;
     default:
       return false;
@@ -70,7 +71,8 @@ bool InitializeStaticGLBindings(GLImplementation implementation) {
     case kGLImplementationEGLGLES2:
       return InitializeStaticEGLInternal();
     case kGLImplementationMockGL:
-      SetGLImplementation(kGLImplementationMockGL);
+    case kGLImplementationStubGL:
+      SetGLImplementation(implementation);
       InitializeStaticGLBindingsGL();
       return true;
     default: