Windows docking should get triggered by pressing against the screen edge

ash/wm/drag_window_resizer.cc

 // 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.
 
 #include "ash/wm/drag_window_resizer.h"
 
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/wm/coordinate_conversion.h"
@@ skipping 92 matching lines @@
 
   GetTarget()->layer()->SetOpacity(details_.initial_opacity);
   drag_window_controller_.reset();
 
   // Check if the destination is another display.
   gfx::Point last_mouse_location_in_screen = last_mouse_location_;
   wm::ConvertPointToScreen(GetTarget()->parent(),
                            &last_mouse_location_in_screen);
   gfx::Screen* screen = Shell::GetScreen();
   const gfx::Display dst_display =
-      screen->GetDisplayNearestPoint(last_mouse_location_in_screen);
-
+      ScreenAsh::FindDisplayContainingPoint(last_mouse_location_in_screen);
+  if (!dst_display.is_valid())

[flackr, 2013/09/06 02:18:43]

What happens in this case? If the drag crossed into another monitor and then
went outside the display (not sure when this happens) wouldn't that leave the
window parented to the first display but in the second monitor's bounds?

[varkha, 2013/09/09 15:38:42]

I think this only happens when you don't --ash-constrain-pointer-to-root. The
window dragged from the right screen to the left and beyond was disappearing.
This was bothering me during development but I left this out of this CL for now.
The alternative as you point out correctly is not much better.

+    return;
   if (dst_display.id() !=
       screen->GetDisplayNearestWindow(GetTarget()->GetRootWindow()).id()) {
     const gfx::Rect dst_bounds =
         ScreenAsh::ConvertRectToScreen(GetTarget()->parent(),
                                        GetTarget()->bounds());
     GetTarget()->SetBoundsInScreen(dst_bounds, dst_display);
   }
 }
 
 void DragWindowResizer::RevertDrag() {
@@ skipping 76 matching lines @@
 
 bool DragWindowResizer::ShouldAllowMouseWarp() {
   return (details_.window_component == HTCAPTION) &&
       !GetTarget()->transient_parent() &&
       (GetTarget()->type() == aura::client::WINDOW_TYPE_NORMAL ||
        GetTarget()->type() == aura::client::WINDOW_TYPE_PANEL);
 }
 
 }  // namespace internal
 }  // namespace ash