Add context to gfx::Screen calls in support of simultaneous desktop+ash

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 "ui/gfx/display.h"
 
 namespace gfx {
 
 // static
-gfx::Display Screen::GetPrimaryDisplay() {
+gfx::Display Screen::GetPrimaryDisplay(gfx::NativeView context) {
   UIScreen* mainScreen = [[UIScreen screens] objectAtIndex:0];
   gfx::Display display(0, gfx::Rect(mainScreen.bounds));
   return display;
 }
 
 // static
-int Screen::GetNumDisplays() {
+int Screen::GetNumDisplays(gfx::NativeView context) {
 #if TARGET_IPHONE_SIMULATOR
   // UIScreen does not reliably return correct results on the simulator.
   return 1;
 #else
   return [[UIScreen screens] count];
 #endif
 }
 
 }  // namespace gfx