Add support for taking partial screenshot using touch

ash/wm/partial_screenshot_view.h

Index: ash/wm/partial_screenshot_view.h
diff --git a/ash/wm/partial_screenshot_view.h b/ash/wm/partial_screenshot_view.h
index a2ca607f2ff88e93c7b3ddcea03bb6c615c073e7..84e636b7dfb6afc47db47b56bb822a97e94eb37e 100644
--- a/ash/wm/partial_screenshot_view.h
+++ b/ash/wm/partial_screenshot_view.h
@@ -38,6 +38,10 @@ class ASH_EXPORT PartialScreenshotView : public views::WidgetDelegateView {
   // Returns the currently selected region.
   gfx::Rect GetScreenshotRect() const;
 
+  void OnSelectionStarted(const gfx::Point& position);
+  void OnSelectionChanged(const gfx::Point& position);
+  void OnSelectionFinished();
+
   // Overridden from views::View:
   virtual gfx::NativeCursor GetCursor(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
@@ -46,6 +50,9 @@ class ASH_EXPORT PartialScreenshotView : public views::WidgetDelegateView {
   virtual bool OnMouseWheel(const ui::MouseWheelEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
 
+  // Overidden from ui::EventHandler:
+  virtual void OnGestureEvent(ui::GestureEvent* event);
+
   bool is_dragging_;
   gfx::Point start_position_;
   gfx::Point current_position_;