clang/win: Let some chromium_code targets build with -Wextra.

ui/native_theme/native_theme_win.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 "ui/native_theme/native_theme_win.h"
 
 #include <windows.h>
 #include <uxtheme.h>
 #include <vsstyle.h>
 #include <vssym32.h>
@@ skipping 338 matching lines @@
   }
 }
 
 void NativeThemeWin::OnSysColorChange() {
   UpdateSystemColors();
   is_using_high_contrast_valid_ = false;
   NotifyObservers();
 }
 
 void NativeThemeWin::UpdateSystemColors() {
-  for (int i = 0; i < arraysize(kSystemColors); ++i) {
-    system_colors_[kSystemColors[i]] =
-        color_utils::GetSysSkColor(kSystemColors[i]);
-  }
+  for (int kSystemColor : kSystemColors)
+    system_colors_[kSystemColor] = color_utils::GetSysSkColor(kSystemColor);
 }
 
 void NativeThemeWin::PaintDirect(SkCanvas* canvas,
                                  Part part,
                                  State state,
                                  const gfx::Rect& rect,
                                  const ExtraParams& extra) const {
   skia::ScopedPlatformPaint scoped_platform_paint(canvas);
   HDC hdc = scoped_platform_paint.GetPlatformSurface();
 
@@ skipping 1692 matching lines @@
     break;
   case LAST:
     NOTREACHED();
     break;
   }
   theme_handles_[theme_name] = handle;
   return handle;
 }
 
 }  // namespace ui