Windows docking should get triggered by pressing against the screen edge

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 bd5f719ae482d1d78be1c20d70fd0895e3eb0703..b4cae25739b8dc244593816fa3af0a1a5e2629e5 100644
--- a/ash/wm/workspace/snap_sizer.h
+++ b/ash/wm/workspace/snap_sizer.h
@@ -19,6 +19,8 @@ class Window;
 namespace ash {
 namespace internal {
 
+class DockedWindowLayoutManager;
+
 // SnapSizer is responsible for determining the resulting bounds of a window
 // that is being snapped to the left or right side of the screen.
 // The bounds used in this class are in the container's coordinates.
@@ -31,6 +33,7 @@ class ASH_EXPORT SnapSizer {
 
   enum InputType {
     TOUCH_MAXIMIZE_BUTTON_INPUT,
+    WORKSPACE_DRAG_INPUT,
     OTHER_INPUT
   };
 
@@ -63,6 +66,13 @@ class ASH_EXPORT SnapSizer {
   // For unit test purposes this function is not private.
   gfx::Rect GetTargetBoundsForSize(size_t size_index) const;
 
+  // Returns true when snapping sequence is at its last (docking) step.
+  bool ShouldDockWindow() const;
+
+  // Returns true when a window can be docked. Windows cannot be docked at the
+  // edge used by the launcher shelf or the edge opposite from existing dock.
+  static bool CanDockWindow(aura::Window* window, SnapSizer::Edge edge);
+
  private:
   // Calculates the amount to increment by. This returns one of -1, 0 or 1 and
   // is intended to by applied to |size_index_|. |x| is the current
@@ -81,6 +91,10 @@ class ASH_EXPORT SnapSizer {
   // Returns true if the specified point is along the edge of the screen.
   bool AlongEdge(int x) const;
 
+  // Dock when a window is at its last step in snapping sequence, undock
+  // otherwise.
+  void UpdateDockedState();
+
   // Window being snapped.
   aura::Window* window_;
 
@@ -118,8 +132,12 @@ class ASH_EXPORT SnapSizer {
   const InputType input_type_;
 
   // A list of usable window widths for size. This gets created when the
-  // sizer gets created.
-  const std::vector<int> usable_width_;
+  // sizer gets created. Possible last 0 entry indicates that computing bounds
+  // needs to be delegated to DockedWindowLayoutManager.
+  std::vector<int> usable_width_;
+
+  // Dock container window layout manager.
+  DockedWindowLayoutManager* dock_layout_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapSizer);
 };