ash: Add accelerator for snapping windows left/right.

ash/wm/workspace/snap_sizer.h

Index: ash/wm/workspace/snap_sizer.h
diff --git a/ash/wm/workspace/snap_sizer.h b/ash/wm/workspace/snap_sizer.h
index e389de7a70dd88fbb706496394dd4315beb8a16d..145e4e58b2cbe1e278b1b810ba533024b853e8ce 100644
--- a/ash/wm/workspace/snap_sizer.h
+++ b/ash/wm/workspace/snap_sizer.h
@@ -38,6 +38,10 @@ class ASH_EXPORT SnapSizer {
   // Bounds to position the window at.
   const gfx::Rect& target_bounds() const { return target_bounds_; }
 
+  // Returns the appropriate snap bounds (e.g. if a window is already snapped,
+  // then it returns the next snap-bounds).
+  gfx::Rect GetSnapBounds(const gfx::Rect& bounds);
+
  private:
   // Calculates the amount to increment by. This returns one of -1, 0 or 1 and
   // is intended to by applied to |percent_index_|. |x| is the current
@@ -53,6 +57,8 @@ class ASH_EXPORT SnapSizer {
   // Returns the target bounds based on the edge and |percent_index_|.
   gfx::Rect GetTargetBounds() const;
 
+  gfx::Rect GetTargetBoundsForPercent(int percent_index) const;
+
   // Returns true if the specified point is along the edge of the screen.
   bool AlongEdge(int x) const;