gfx::Screen: Replace GetWindowUnderCursor() with IsWindowUnderCursor().

ui/gfx/screen_ios.mm

 // 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 "ui/gfx/screen.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #include "ui/gfx/display.h"
 
 namespace {
 
 class ScreenIos : public gfx::Screen {
   gfx::Point GetCursorScreenPoint() override {
     NOTIMPLEMENTED();
     return gfx::Point(0, 0);
   }
 
-  gfx::NativeWindow GetWindowUnderCursor() override {
+  bool IsWindowUnderCursor(gfx::NativeWindow window) override {
     NOTIMPLEMENTED();
-    return gfx::NativeWindow();
+    return false;
   }
 
   gfx::NativeWindow GetWindowAtScreenPoint(const gfx::Point& point) override {
     NOTIMPLEMENTED();
     return gfx::NativeWindow();
   }
 
   int GetNumDisplays() const override {
 #if TARGET_IPHONE_SIMULATOR
     // UIScreen does not reliably return correct results on the simulator.
@@ skipping 46 matching lines @@
 
 }  // namespace
 
 namespace gfx {
 
 Screen* CreateNativeScreen() {
   return new ScreenIos;
 }
 
 }  // namespace gfx