ui: Allow individual test suites to opt-out of the TestCompositor.

ui/gl/gl_implementation.h

Index: ui/gl/gl_implementation.h
diff --git a/ui/gl/gl_implementation.h b/ui/gl/gl_implementation.h
index f163e07c1505c3b3ccf91660bbe117a237f18f98..6f4eaf7fa0d70f9932aee983c5741e7530d409fc 100644
--- a/ui/gl/gl_implementation.h
+++ b/ui/gl/gl_implementation.h
@@ -56,6 +56,9 @@ void InitializeDebugGLBindings();
 // null draw bindings default to enabled, so that draw operations do nothing.
 void InitializeNullDrawGLBindings();
 
+// TODO(danakj): Remove this when all test suites are using null-draw.
+GL_EXPORT bool HasInitializedNullDrawGLBindings();
+
 // Once initialized, instantiating this turns the stub methods for drawing
 // operations off allowing drawing will occur while the object is alive.
 class GL_EXPORT DisableNullDrawGLBindings {