Add scale factor and 2x resources from webkit and plumb through to ContentClient.

ui/compositor/test/compositor_test_support.cc

Index: ui/compositor/test/compositor_test_support.cc
diff --git a/ui/compositor/test/compositor_test_support.cc b/ui/compositor/test/compositor_test_support.cc
index 6134f548e0e5ec699b2a28eb8858a77ea011ba21..07c2ce708f2eb468a35200b803e11293f26e575f 100644
--- a/ui/compositor/test/compositor_test_support.cc
+++ b/ui/compositor/test/compositor_test_support.cc
@@ -21,6 +21,11 @@ class CompositorTestPlatformSupport:
     return base::StringPiece();
   }
 
+  virtual base::StringPiece GetImageResource(int resource_id,
+                                             float scale_factor) OVERRIDE {
+    return base::StringPiece();
+  }
+
   virtual void GetPlugins(
       bool refresh, std::vector<webkit::WebPluginInfo>* plugins) OVERRIDE {
   }