[Android] Isolate OverscrollRefresh from device density

content/browser/android/overscroll_refresh.h

 // Copyright 2014 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_ANDROID_OVERSCROLL_REFRESH_H_
 #define CONTENT_BROWSER_ANDROID_OVERSCROLL_REFRESH_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
@@ skipping 26 matching lines @@
 
 // Simple pull-to-refresh styled effect. Listens to scroll events, conditionally
 // activating when:
 //   1) The scroll begins when the page has no vertical scroll offset.
 //   2) The page doesn't consume the initial scroll events.
 //   3) The initial scroll direction is upward.
 // The actual page reload action is triggered only when the effect is active
 // and beyond a particular threshold when released.
 class CONTENT_EXPORT OverscrollRefresh {
  public:
+  // Both |resource_manager| and |client| must not be null.
+  // |target_drag_offset_pixels| is the threshold beyond which the effect
+  // will trigger a refresh action when released.
   OverscrollRefresh(ui::SystemUIResourceManager* resource_manager,
-                    OverscrollRefreshClient* client);
+                    OverscrollRefreshClient* client,
+                    float target_drag_offset_pixels);
   ~OverscrollRefresh();
 
   // Scroll event stream listening methods.
   void OnScrollBegin();
   void OnScrollEnd(const gfx::Vector2dF& velocity);
 
   // Scroll ack listener. The effect will only be activated if the initial
   // updates go unconsumed.
   void OnScrollUpdateAck(bool was_consumed);
 
@@ skipping 35 matching lines @@
 
   class Effect;
   scoped_ptr<Effect> effect_;
 
   DISALLOW_COPY_AND_ASSIGN(OverscrollRefresh);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ANDROID_OVERSCROLL_REFRESH_H_