Refactor Scroll Customization to share cc::ScrollStateData with blink.

cc/input/scroll_state_data.h

Index: cc/input/scroll_state_data.h
diff --git a/cc/input/scroll_state_data.h b/cc/input/scroll_state_data.h
index 302970bd08d7f898390e98aadfd920bfdc9b51b5..d0f129733c1eb434bf2713fbd617b059a6e711d5 100644
--- a/cc/input/scroll_state_data.h
+++ b/cc/input/scroll_state_data.h
@@ -5,6 +5,8 @@
 #ifndef CC_INPUT_SCROLL_STATE_DATA_H_
 #define CC_INPUT_SCROLL_STATE_DATA_H_
 
+#include <stdint.h>
+
 #include <list>
 
 #include "cc/base/cc_export.h"
@@ -13,7 +15,7 @@ namespace cc {
 
 class LayerImpl;
 
-struct CC_EXPORT ScrollStateData {
+class CC_EXPORT ScrollStateData {
  public:
   ScrollStateData();
   ScrollStateData(double delta_x,
@@ -26,8 +28,10 @@ struct CC_EXPORT ScrollStateData {
                   bool is_in_inertial_phase,
                   bool is_ending,
                   bool should_propagate,
-                  bool delta_consumed_for_scroll_sequence,
-                  bool is_direct_manipulation);
+                  bool from_user_input,
+                  bool is_direct_manipulation,
+                  double delta_granularity,
+                  bool delta_consumed_for_scroll_sequence);
   // Scroll delta in viewport coordinates (DIP).
   double delta_x;
   double delta_y;
@@ -43,15 +47,17 @@ struct CC_EXPORT ScrollStateData {
   bool is_ending;
 
   bool should_propagate;
+  bool from_user_input;
 
-  // The last layer to respond to a scroll, or null if none exists.
-  LayerImpl* current_native_scrolling_layer;
   // Whether the scroll sequence has had any delta consumed, in the
   // current frame, or any child frames.
   bool delta_consumed_for_scroll_sequence;
   // True if the user interacts directly with the display, e.g., via
   // touch.
   bool is_direct_manipulation;
+  // Minimum amount this input device can scroll.
+  double delta_granularity;
+
   // TODO(tdresser): ScrollState shouldn't need to keep track of whether or not
   // this ScrollState object has caused a scroll. Ideally, any native scroller
   // consuming delta has caused a scroll. Currently, there are some cases where
@@ -60,6 +66,23 @@ struct CC_EXPORT ScrollStateData {
   // of |caused_scroll_*_|. See crbug.com/510045 for details.
   bool caused_scroll_x;
   bool caused_scroll_y;
+
+  LayerImpl* current_native_scrolling_layer() const;
+  void set_current_native_scrolling_layer(
+      LayerImpl* current_native_scrolling_layer);
+  uint64_t current_native_scrolling_element() const;
+  void set_current_native_scrolling_element(uint64_t element_id);
+
+ private:
+  // Only one of current_native_scrolling_layer_ and
+  // current_native_scrolling_element_ may be non-null at a time. Whenever
+  // possible, we should store the layer.
+
+  // The last layer to respond to a scroll, or null if none exists.
+  LayerImpl* current_native_scrolling_layer_;
+  // The id of the last native element to respond to a scroll, or 0 if none
+  // exists.
+  uint64_t current_native_scrolling_element_;
 };
 
 }  // namespace cc