Mac: Don't repaint scrollbars every frame

cc/test/fake_layer_tree_host.h

Index: cc/test/fake_layer_tree_host.h
diff --git a/cc/test/fake_layer_tree_host.h b/cc/test/fake_layer_tree_host.h
index 5927dec6bb604d8c440d35c1b9524d98c81e8fa3..5e6bb1026ffdeb1bb95b35d7ca64daa907b24d75 100644
--- a/cc/test/fake_layer_tree_host.h
+++ b/cc/test/fake_layer_tree_host.h
@@ -29,6 +29,7 @@ class FakeLayerTreeHost : public LayerTreeHost {
 
   ~FakeLayerTreeHost() override;
 
+  const RendererCapabilities& GetRendererCapabilities() const override;
   void SetNeedsCommit() override;
   void SetNeedsUpdateLayers() override {}
   void SetNeedsFullTreeSync() override {}
@@ -54,6 +55,11 @@ class FakeLayerTreeHost : public LayerTreeHost {
 
   bool needs_commit() { return needs_commit_; }
 
+  void set_renderer_capabilities(const RendererCapabilities& capabilities) {
+    renderer_capabilities_set = true;
+    renderer_capabilities = capabilities;
+  }
+
  protected:
   FakeLayerTreeHost(FakeLayerTreeHostClient* client,
                     LayerTreeHost::InitParams* params);
@@ -64,6 +70,9 @@ class FakeLayerTreeHost : public LayerTreeHost {
   TestSharedBitmapManager manager_;
   FakeLayerTreeHostImpl host_impl_;
   bool needs_commit_;
+
+  bool renderer_capabilities_set;
+  RendererCapabilities renderer_capabilities;
 };
 
 }  // namespace cc