Scrollbar fade animation broken on Android regression resolved.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 6d97f27511c28112ed55508cc8e9e0b4ccf27f20..6722a7c0cc4ab49d5d6099b0306ce50875758f34 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -131,6 +131,34 @@ class LayerTreeHostImplClient {
   virtual ~LayerTreeHostImplClient() {}
 };
 
+// Used to cache scroll related variables that get reset while clearing
+// the currently scrolling layer. Cached values are restored in case of a
+// scrollBegin in inertial phase (fling) to latch the fling to its
+// corresponding scroll event.
+class ScrollingVariablesState {
+ public:
+  ScrollingVariablesState() {
+    ScrollingVariablesState(false, false, gfx::Vector2dF());
+  }
+  ScrollingVariablesState(bool did_lock_scrolling_layer,
+                          bool scroll_affects_scroll_handler,
+                          gfx::Vector2dF accumulated_root_overscroll)
+      : did_lock_scrolling_layer_(did_lock_scrolling_layer),
+        scroll_affects_scroll_handler_(scroll_affects_scroll_handler),
+        accumulated_root_overscroll_(accumulated_root_overscroll) {}
+
+  bool didLockScrollingLayer() { return did_lock_scrolling_layer_; }
+  bool scrollAffectsScrollHandler() { return scroll_affects_scroll_handler_; }
+  gfx::Vector2dF accumulatedRootOverscroll() {
+    return accumulated_root_overscroll_;
+  }
+
+ private:
+  bool did_lock_scrolling_layer_;
+  bool scroll_affects_scroll_handler_;
+  gfx::Vector2dF accumulated_root_overscroll_;
+};
+
 // LayerTreeHostImpl owns the LayerImpl trees as well as associated rendering
 // state.
 class CC_EXPORT LayerTreeHostImpl
@@ -701,6 +729,13 @@ class CC_EXPORT LayerTreeHostImpl
   void SetCompositorContextVisibility(bool is_visible);
   void SetWorkerContextVisibility(bool is_visible);
 
+  // Cache & restore variables that get reset in ClearCurrentlyScrollingLayer.
+  // This is used to restore the variables' values in a scrollBegin event
+  // that is in inertial phase (a fling) to latch the event to its
+  // corresponding scroller.
+  void CacheScrollingVariablesState();
+  void RestoreCachedScrollingVariablesState();
+
   using UIResourceMap = std::unordered_map<UIResourceId, UIResourceData>;
   UIResourceMap ui_resource_map_;
 
@@ -841,6 +876,8 @@ class CC_EXPORT LayerTreeHostImpl
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
+  ScrollingVariablesState cached_scrolling_variables_state_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };