Coalesce scrollUpdate and pinchUpdate on gesture_event queue

content/browser/renderer_host/gesture_event_filter.h

Index: content/browser/renderer_host/gesture_event_filter.h
diff --git a/content/browser/renderer_host/gesture_event_filter.h b/content/browser/renderer_host/gesture_event_filter.h
index 229904ea8d705d904cd3ca93947610ef25fa694f..ac101e4beb771491d6872ad7b7d3f48203f2b6c7 100644
--- a/content/browser/renderer_host/gesture_event_filter.h
+++ b/content/browser/renderer_host/gesture_event_filter.h
@@ -11,6 +11,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/timer.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
+#include "ui/gfx/transform.h"
 
 namespace content {
 class MockRenderWidgetHost;
@@ -78,8 +79,9 @@ class GestureEventFilter {
   // hence that event should be handled now.
   bool ShouldHandleEventNow();
 
-  // Merge or append a GestureScrollUpdate into the coalescing queue.
-  void MergeOrInsertScrollEvent(
+  // Merge or append a GestureScrollUpdate or GesturePinchUpdate into
+  // the coalescing queue.
+  void MergeOrInsertScrollAndPinchEvent(
        const WebKit::WebGestureEvent& gesture_event);
 
   // Sub-filter for removing bounces from in-progress scrolls.
@@ -91,6 +93,18 @@ class GestureEventFilter {
   bool ShouldForwardForTapDeferral(
       const WebKit::WebGestureEvent& gesture_event);
 
+  // Whether the event_in_queue is GesturePinchUpdate or
+  // GestureScrollUpdate and it has the same modifiers as the
+  // new event.
+  bool ShouldTryMerging(const WebKit::WebGestureEvent& new_event,
+      const WebKit::WebGestureEvent& event_in_queue);
+
+  // Returns the transform matrix corresponding to the gesture event.
+  // Assumes the gesture event sent is either GestureScrollUpdate or
+  // GesturePinchUpdate. Returns the identity matrix otherwise.
+  gfx::Transform GetTransformForEvent(
+      const WebKit::WebGestureEvent& gesture_event);
+
   // Only a RenderWidgetHostViewImpl can own an instance.
   RenderWidgetHostImpl* render_widget_host_;
 
@@ -101,6 +115,14 @@ class GestureEventFilter {
   // True if a GestureScrollUpdate sequence is in progress.
   bool scrolling_in_progress_;
 
+  // True if two related gesture events were sent before without waiting
+  // for an ACK, so the next gesture ACK should be ignored.
+  bool ignore_next_ack_;
+
+  // Transform that holds the combined transform matrix for the current
+  // scroll-pinch sequence at the end of the queue.
+  gfx::Transform combined_scroll_pinch_;
+
   // Timer to release a previously deferred GestureTapDown event.
   base::OneShotTimer<GestureEventFilter> send_gtd_timer_;