Refactoring: Extract gesture event filtering into helper class.

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
new file mode 100644
index 0000000000000000000000000000000000000000..aff3b318e35ebde4b9d0f5e3cb36b530e6634750
--- /dev/null
+++ b/content/browser/renderer_host/gesture_event_filter.h
@@ -0,0 +1,82 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_GESTURE_EVENT_FILTER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_GESTURE_EVENT_FILTER_H_
+
+#include <deque>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
+
+class MockRenderWidgetHost;
+
+namespace content {
+
+class RenderWidgetHostImpl;
+class TapSuppressionController;
+
+// Manages a queue of in-progress |WebGestureEvent| instances filtering,
+// coalescing or discarding them as required to maximize the chance that
+// the event stream can be handled entirely by the compositor thread.
+class GestureEventFilter {
+ public:
+  explicit GestureEventFilter(RenderWidgetHostImpl*);
+  ~GestureEventFilter();
+
+  // Returns |true| if the caller should immediately forward the provided
+  // |WebGestureEvent| argument to the renderer.
+  bool ShouldForward(const WebKit::WebGestureEvent&);
+
+  // Indicate that calling RenderWidgetHostImpl has received an acknowledgement
+  // from the renderer with state |processed| and event |type|. May send events
+  // if the queue is not empty.
+  void ProcessGestureAck(bool processed, int type);
+
+  // Reset the state of the filter as would be needed when the Renderer exits.
+  void Reset();
+
+  // Set the state of the |fling_in_progress_| field to indicate that a fling is
+  // definitely not in progress.
+  void FlingHasBeenHalted();
+
+  // Return the |TapSuppressionController| instance.
+  TapSuppressionController* GetTapSuppressionController();
+
+ private:
+  friend class ::MockRenderWidgetHost;
+
+  // Returns |true| if the given GestureFlingCancel should be discarded
+  // as unnecessary.
+  bool ShouldDiscardFlingCancelEvent(
+    const WebKit::WebGestureEvent& gesture_event);
+
+  // Only a RenderWidgetHostViewImpl can own an instance.
+  RenderWidgetHostImpl* render_widget_host_;
+
+  // True if a GestureFlingStart is in progress on the renderer.
+  bool fling_in_progress_;
+
+  // (Similar to |mouse_wheel_pending_|.). True if gesture event was sent and
+  // we are waiting for a corresponding ack.
+  bool gesture_event_pending_;
+
+  // An object tracking the state of touchpad action on the delivery of mouse
+  // events to the renderer to filter mouse actiosn immediately after a touchpad
+  // fling canceling tap.
+  scoped_ptr<TapSuppressionController> tap_suppression_controller_;
+
+  typedef std::deque<WebKit::WebGestureEvent> GestureEventQueue;
+
+  // (Similar to |coalesced_mouse_wheel_events_|.) GestureScrollUpdate events
+  // are coalesced by merging deltas in a similar fashion as wheel events.
+  GestureEventQueue coalesced_gesture_events_;
+
+  DISALLOW_COPY_AND_ASSIGN(GestureEventFilter);
+};
+
+} // namespace content
+
+#endif // CONTENT_BROWSER_RENDERER_HOST_GESTURE_EVENT_FILTER_H_