cc: Cleanup - remove unused 'Webkit' forward declaration.

cc/test/layer_tree_test.h

Index: cc/test/layer_tree_test.h
diff --git a/cc/test/layer_tree_test.h b/cc/test/layer_tree_test.h
index ba40e350d2dee3df9f0c221227a9485dc3e5d87e..4e38ae6bb6b094b8d7a3793f2282a57bb139aba9 100644
--- a/cc/test/layer_tree_test.h
+++ b/cc/test/layer_tree_test.h
@@ -12,10 +12,6 @@
 #include "cc/trees/layer_tree_host_impl.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace Webkit {
-class WebGraphicsContext3D;
-}
-
 namespace cc {
 class FakeExternalBeginFrameSource;
 class FakeLayerTreeHostClient;