Double clicking the resize handle should expand window along that axis.

ui/aura/test/test_window_delegate.h

 // Copyright (c) 2012 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 UI_AURA_TEST_TEST_WINDOW_DELEGATE_H_
 #define UI_AURA_TEST_TEST_WINDOW_DELEGATE_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/aura/window_delegate.h"
 
 namespace aura {
 namespace test {
 
 // WindowDelegate implementation with all methods stubbed out.
 class TestWindowDelegate : public WindowDelegate {
  public:
   TestWindowDelegate();
   virtual ~TestWindowDelegate();
 
+  void set_window_component(int window_component) {
+    window_component_ = window_component;
+  }
+
   // Overridden from WindowDelegate:
   virtual gfx::Size GetMinimumSize() const OVERRIDE;
   virtual void OnBoundsChanged(const gfx::Rect& old_bounds,
                                const gfx::Rect& new_bounds) OVERRIDE;
   virtual void OnFocus() OVERRIDE;
   virtual void OnBlur() OVERRIDE;
   virtual bool OnKeyEvent(KeyEvent* event) OVERRIDE;
   virtual gfx::NativeCursor GetCursor(const gfx::Point& point) OVERRIDE;
   virtual int GetNonClientComponent(const gfx::Point& point) const OVERRIDE;
   virtual bool OnMouseEvent(MouseEvent* event) OVERRIDE;
   virtual ui::TouchStatus OnTouchEvent(TouchEvent* event) OVERRIDE;
   virtual ui::GestureStatus OnGestureEvent(GestureEvent* event) OVERRIDE;
   virtual bool CanFocus() OVERRIDE;
   virtual void OnCaptureLost() OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
   virtual void OnWindowDestroying() OVERRIDE;
   virtual void OnWindowDestroyed() OVERRIDE;
   virtual void OnWindowVisibilityChanged(bool visible) OVERRIDE;
 
  private:
+  int window_component_;
+
   DISALLOW_COPY_AND_ASSIGN(TestWindowDelegate);
 };
 
 // A simple WindowDelegate implementation for these tests. It owns itself
 // (deletes itself when the Window it is attached to is destroyed).
 class ColorTestWindowDelegate : public TestWindowDelegate {
  public:
   explicit ColorTestWindowDelegate(SkColor color);
   virtual ~ColorTestWindowDelegate();
 
   ui::KeyboardCode last_key_code() const { return last_key_code_; }
 
   // Overridden from TestWindowDelegate:
   virtual bool OnKeyEvent(KeyEvent* event) OVERRIDE;
   virtual void OnWindowDestroyed() OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
 
  private:
   SkColor color_;
   ui::KeyboardCode last_key_code_;
 
   DISALLOW_COPY_AND_ASSIGN(ColorTestWindowDelegate);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_TEST_WINDOW_DELEGATE_H_