cc: Add a rails argument to InputHandler::ScrollBy

cc/input/input_handler.h

 // Copyright 2011 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 CC_INPUT_INPUT_HANDLER_H_
 #define CC_INPUT_INPUT_HANDLER_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
@@ skipping 56 matching lines @@
   // entries.
   enum ScrollStatus {
     SCROLL_ON_MAIN_THREAD = 0,
     SCROLL_STARTED,
     SCROLL_IGNORED,
     SCROLL_UNKNOWN,
     // This must be the last entry.
     ScrollStatusCount
   };
   enum ScrollInputType { GESTURE, WHEEL, NON_BUBBLING_GESTURE };
+  enum RailsMode {
+    RAILS_MODE_FREE,
+    RAILS_MODE_HORIZONTAL,
+    RAILS_MODE_VERTICAL
+  };
 
   // Binds a client to this handler to receive notifications. Only one client
   // can be bound to an InputHandler. The client must live at least until the
   // handler calls WillShutdown() on the client.
   virtual void BindToClient(InputHandlerClient* client) = 0;
 
   // Selects a layer to be scrolled at a given point in viewport (logical
   // pixel) coordinates. Returns SCROLL_STARTED if the layer at the coordinates
   // can be scrolled, SCROLL_ON_MAIN_THREAD if the scroll event should instead
   // be delegated to the main thread, or SCROLL_IGNORED if there is nothing to
   // be scrolled at the given coordinates.
   virtual ScrollStatus ScrollBegin(const gfx::Point& viewport_point,
                                    ScrollInputType type) = 0;
 
   virtual ScrollStatus ScrollAnimated(const gfx::Point& viewport_point,
                                       const gfx::Vector2dF& scroll_delta) = 0;
 
   // Scroll the selected layer starting at the given position. If the scroll
   // type given to ScrollBegin was a gesture, then the scroll point and delta
   // should be in viewport (logical pixel) coordinates. Otherwise they are in
   // scrolling layer's (logical pixel) space. If there is no room to move the
   // layer in the requested direction, its first ancestor layer that can be
   // scrolled will be moved instead. The return value's |did_scroll| field is
   // set to false if no layer can be moved in the requested direction at all,
   // and set to true if any layer is moved.
   // If the scroll delta hits the root layer, and the layer can no longer move,
   // the root overscroll accumulated within this ScrollBegin() scope is reported
   // in the return value's |accumulated_overscroll| field.
   // Should only be called if ScrollBegin() returned SCROLL_STARTED.
-  virtual InputHandlerScrollResult ScrollBy(
-      const gfx::Point& viewport_point,
-      const gfx::Vector2dF& scroll_delta) = 0;
+  virtual InputHandlerScrollResult ScrollBy(const gfx::Point& viewport_point,
+                                            const gfx::Vector2dF& scroll_delta,
+                                            RailsMode rails_mode) = 0;
 
   virtual bool ScrollVerticallyByPage(const gfx::Point& viewport_point,
                                       ScrollDirection direction) = 0;
 
   // Returns SCROLL_STARTED if a layer was being actively being scrolled,
   // SCROLL_IGNORED if not.
   virtual ScrollStatus FlingScrollBegin() = 0;
 
   virtual void MouseMoveAt(const gfx::Point& mouse_position) = 0;
 
@@ skipping 43 matching lines @@
   InputHandler() {}
   virtual ~InputHandler() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(InputHandler);
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_INPUT_HANDLER_H_