cc: Add null checks for GrContext created by ContextProviderCommandBuffer.

cc/test/fake_output_surface.h

Index: cc/test/fake_output_surface.h
diff --git a/cc/test/fake_output_surface.h b/cc/test/fake_output_surface.h
index 6028cade045a8ebee630896f4d3b6fbd60fc2997..7041a447f8e187f1403bc71c4821ba66211d28d3 100644
--- a/cc/test/fake_output_surface.h
+++ b/cc/test/fake_output_surface.h
@@ -29,7 +29,8 @@ class FakeOutputSurface : public OutputSurface {
 
   static scoped_ptr<FakeOutputSurface> Create3d(
       scoped_refptr<ContextProvider> context_provider) {
-    return make_scoped_ptr(new FakeOutputSurface(context_provider, false));
+    return make_scoped_ptr(new FakeOutputSurface(
+        context_provider, TestContextProvider::Create(), false));
   }
 
   static scoped_ptr<FakeOutputSurface> Create3d(
@@ -41,8 +42,9 @@ class FakeOutputSurface : public OutputSurface {
 
   static scoped_ptr<FakeOutputSurface> Create3d(
       scoped_ptr<TestWebGraphicsContext3D> context) {
-    return make_scoped_ptr(new FakeOutputSurface(
-        TestContextProvider::Create(context.Pass()), false));
+    return make_scoped_ptr(
+        new FakeOutputSurface(TestContextProvider::Create(context.Pass()),
+                              TestContextProvider::Create(), false));
   }
 
   static scoped_ptr<FakeOutputSurface> CreateSoftware(