cc: Don't use partial updates for scrollbars when they are not allowed.

cc/layer_tree_settings.h

Index: cc/layer_tree_settings.h
diff --git a/cc/layer_tree_settings.h b/cc/layer_tree_settings.h
index 847795f810fcc068f26afb6edc130650cfe0fa54..6f0f7bebc5a572dcd90487d87255a40ff2e9c742 100644
--- a/cc/layer_tree_settings.h
+++ b/cc/layer_tree_settings.h
@@ -29,6 +29,7 @@ class CC_EXPORT LayerTreeSettings {
   bool showOverdrawInTracing;
   bool canUseLCDText;
   bool shouldClearRootRenderPass;
+  bool useLinearFadeScrollbarAnimator;
   double refreshRate;
   size_t maxPartialTextureUpdates;
   size_t numRasterThreads;