Allow the cursor to warp even when a window is dragged

ash/wm/coordinate_conversion.h

Index: ash/wm/coordinate_conversion.h
diff --git a/ash/wm/coordinate_conversion.h b/ash/wm/coordinate_conversion.h
new file mode 100644
index 0000000000000000000000000000000000000000..40b6fb1d187649e17ee6b679d033694b4f3073ff
--- /dev/null
+++ b/ash/wm/coordinate_conversion.h
@@ -0,0 +1,46 @@
+// 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 ASH_WM_COORDINATE_CONVERSION_H_
+#define ASH_WM_COORDINATE_CONVERSION_H_
+
+#include "ash/ash_export.h"
+
+#include "ui/gfx/point.h"
+
+namespace aura {
+class RootWindow;
+class Window;
+}  // namespace gfx
+
+namespace gfx {
+class Rect;
+}  // namespace gfx
+
+namespace ash {
+namespace wm {
+
+// Returns the RootWindow at |point| in the virtual screen coordinates.
+// Returns NULL if the root window does not exist at the given
+// point.
+ASH_EXPORT aura::RootWindow* GetRootWindowAt(const gfx::Point& point);
+
+// Returns the RootWindow that shares the most area with |rect| in
+// the virtual scren coordinates.
+ASH_EXPORT aura::RootWindow* GetRootWindowMatching(const gfx::Rect& rect);
+
+// Gets the root window at |location| in |window|'s coordinates. This function
+// just returns a pair of |window->GetRootWindow()| and location in the root

[sky, 2012/08/03 17:07:18]

remove just

[Yusuke Sato, 2012/08/03 23:18:45]

Done.

+// window's coordinate unless the cursor is captured by the root window (so you
+// don't want to call the function when it's not captured). When it's captured,

[sky, 2012/08/03 17:07:18]

I'm confused by this restriction, which means it's going to be error prone. Why
can't this function work consistently all the time?

[Yusuke Sato, 2012/08/03 23:18:45]

Sorry, the comment was very confusing. It's safe to call the function when the
mouse is not captured. Revised the comment to make it clear. 

+// the function tries to find an actual root window where the cursor is
+// currently on in a platform specific way, and returns the root window along
+// with the location in the actual root window's coordinates.
+ASH_EXPORT std::pair<aura::RootWindow*, gfx::Point>
+GetRootWindowRelativeToWindow(aura::Window* window, const gfx::Point& location);
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COORDINATE_CONVERSION_H_