Mac: Use [NSArray firstObject] for [NSScreen screens]

chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm

 // Copyright 2013 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 "chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h"
 
 #include "base/command_line.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/sdk_forward_declarations.h"
@@ skipping 39 matching lines @@
 - (BOOL)_isTitleHidden;
 @end
 
 namespace {
 
 const int kActivateThrottlePeriodSeconds = 2;
 
 NSRect GfxToCocoaBounds(gfx::Rect bounds) {
   typedef AppWindow::BoundsSpecification BoundsSpecification;
 
-  NSRect main_screen_rect = [[[NSScreen screens] objectAtIndex:0] frame];
+  NSRect main_screen_rect = [[[NSScreen screens] firstObject] frame];
 
   // If coordinates are unspecified, center window on primary screen.
   if (bounds.x() == BoundsSpecification::kUnspecifiedPosition)
     bounds.set_x(floor((NSWidth(main_screen_rect) - bounds.width()) / 2));
   if (bounds.y() == BoundsSpecification::kUnspecifiedPosition)
     bounds.set_y(floor((NSHeight(main_screen_rect) - bounds.height()) / 2));
 
   // Convert to Mac coordinates.
   NSRect cocoa_bounds = NSRectFromCGRect(bounds.ToCGRect());
   cocoa_bounds.origin.y = NSHeight(main_screen_rect) - NSMaxY(cocoa_bounds);
@@ skipping 374 matching lines @@
 bool NativeAppWindowCocoa::IsFullscreenOrPending() const {
   return is_fullscreen_;
 }
 
 gfx::NativeWindow NativeAppWindowCocoa::GetNativeWindow() const {
   return window();
 }
 
 gfx::Rect NativeAppWindowCocoa::GetRestoredBounds() const {
   // Flip coordinates based on the primary screen.
-  NSScreen* screen = [[NSScreen screens] objectAtIndex:0];
+  NSScreen* screen = [[NSScreen screens] firstObject];
   NSRect frame = restored_bounds_;
   gfx::Rect bounds(frame.origin.x, 0, NSWidth(frame), NSHeight(frame));
   bounds.set_y(NSHeight([screen frame]) - NSMaxY(frame));
   return bounds;
 }
 
 ui::WindowShowState NativeAppWindowCocoa::GetRestoredState() const {
   if (IsMaximized())
     return ui::SHOW_STATE_MAXIMIZED;
   if (IsFullscreen())
     return ui::SHOW_STATE_FULLSCREEN;
   return ui::SHOW_STATE_NORMAL;
 }
 
 gfx::Rect NativeAppWindowCocoa::GetBounds() const {
   // Flip coordinates based on the primary screen.
-  NSScreen* screen = [[NSScreen screens] objectAtIndex:0];
+  NSScreen* screen = [[NSScreen screens] firstObject];
   NSRect frame = [window() frame];
   gfx::Rect bounds(frame.origin.x, 0, NSWidth(frame), NSHeight(frame));
   bounds.set_y(NSHeight([screen frame]) - NSMaxY(frame));
   return bounds;
 }
 
 void NativeAppWindowCocoa::Show() {
   if (is_hidden_with_app_) {
     apps::ExtensionAppShimHandler::UnhideWithoutActivationForWindow(
         app_window_);
@@ skipping 197 matching lines @@
 SkColor NativeAppWindowCocoa::InactiveFrameColor() const {
   return inactive_frame_color_;
 }
 
 gfx::Insets NativeAppWindowCocoa::GetFrameInsets() const {
   if (!has_frame_)
     return gfx::Insets();
 
   // Flip the coordinates based on the main screen.
   NSInteger screen_height =
-      NSHeight([[[NSScreen screens] objectAtIndex:0] frame]);
+      NSHeight([[[NSScreen screens] firstObject] frame]);
 
   NSRect frame_nsrect = [window() frame];
   gfx::Rect frame_rect(NSRectToCGRect(frame_nsrect));
   frame_rect.set_y(screen_height - NSMaxY(frame_nsrect));
 
   NSRect content_nsrect = [window() contentRectForFrameRect:frame_nsrect];
   gfx::Rect content_rect(NSRectToCGRect(content_nsrect));
   content_rect.set_y(screen_height - NSMaxY(content_nsrect));
 
   return frame_rect.InsetsFrom(content_rect);
@@ skipping 181 matching lines @@
 }
 
 void NativeAppWindowCocoa::UpdateRestoredBounds() {
   if (IsRestored(*this))
     restored_bounds_ = [window() frame];
 }
 
 void NativeAppWindowCocoa::HideWithoutMarkingHidden() {
   [window() orderOut:window_controller_];
 }