Short term workaround to deal with calculation error caused by inverted matrix.

ui/aura/root_window.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_ROOT_WINDOW_H_
 #define UI_AURA_ROOT_WINDOW_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
 #include "ui/aura/aura_export.h"
 #include "ui/aura/client/capture_delegate.h"
 #include "ui/aura/root_window_host_delegate.h"
 #include "ui/aura/window.h"
 #include "ui/base/cursor/cursor.h"
 #include "ui/base/events/event_constants.h"
@@ skipping 265 matching lines @@
   virtual void ReleaseNativeCapture() OVERRIDE;
 
   // Exposes RootWindowHost::QueryMouseLocation() for test purposes.
   bool QueryMouseLocationForTest(gfx::Point* point) const;
 
   // Clears internal mouse state (such as mouse ups should be sent to the same
   // window that ate mouse downs).
   void ClearMouseHandlers();
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(RootWindowTest, KeepTranslatedEventInRoot);
+
   friend class Window;
   friend class TestScreen;
 
   // The parameter for OnWindowHidden() to specify why window is hidden.
   enum WindowHiddenReason {
     WINDOW_DESTROYED,  // Window is destroyed.
     WINDOW_HIDDEN,     // Window is hidden.
     WINDOW_MOVING,     // Window is temporarily marked as hidden due to move
                        // across root windows.
   };
 
   // Updates the event with the appropriate transform for the device scale
   // factor. The RootWindowHostDelegate dispatches events in the physical pixel
   // coordinate. But the event processing from RootWindow onwards happen in
   // device-independent pixel coordinate. So it is necessary to update the event
-  // received from the host.
-  void TransformEventForDeviceScaleFactor(ui::LocatedEvent* event);
+  // received from the host. When |keep_inside_root| is true and the event's
+  // system location is inside host window's bounds, the location will be
+  // kept inside the root window's bounds.
+  void TransformEventForDeviceScaleFactor(ui::LocatedEvent* event,

[sky, 2013/03/21 14:44:12]

out params should be last, so event should be the last parameter.

[oshima, 2013/03/21 15:41:47]

Done.

+                                          bool keep_inside_root);
 
   // Called whenever the mouse moves, tracks the current |mouse_moved_handler_|,
   // sending exited and entered events as its value changes.
   void HandleMouseMoved(const ui::MouseEvent& event, Window* target);
 
   // Dispatches the specified event type (intended for enter/exit) to the
   // |mouse_moved_handler_|.
   void DispatchMouseEnterOrExit(const ui::MouseEvent& event,
                                 ui::EventType type);
 
@@ skipping 132 matching lines @@
   // Note that this should not be confused with the device scale
   // factor, which specfies the pixel density of the display.
   float root_window_scale_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindow);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ROOT_WINDOW_H_