Enable MSVC warning for unused locals.

content/renderer/render_font_warmup_win.cc

 // Copyright 2014 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 "content/public/renderer/render_font_warmup_win.h"
 
 #include <dwrite.h>
 
 #include "base/debug/alias.h"
 #include "base/logging.h"
@@ skipping 173 matching lines @@
   paint_warmup.setTypeface(typeface);
   wchar_t glyph = L'S';
   paint_warmup.measureText(&glyph, 2);
 }
 
 SkFontMgr* GetPreSandboxWarmupFontMgr() {
   if (!g_warmup_fontmgr) {
     IDWriteFactory* factory;
     CreateDirectWriteFactory(&factory);
 
-    IDWriteFontCollection* collection = GetCustomFontCollection(factory);
+    GetCustomFontCollection(factory);
 
     PatchDWriteFactory(factory);
 
     blink::WebFontRendering::setDirectWriteFactory(factory);
     g_warmup_fontmgr = SkFontMgr_New_DirectWrite(factory);
   }
   return g_warmup_fontmgr;
 }
 
 }  // namespace content