Remove disabling of C4267 in 64-bit gn builds

mash/quick_launch/quick_launch_application.cc

 // Copyright 2016 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 "mash/quick_launch/quick_launch_application.h"
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_util.h"
@@ skipping 81 matching lines @@
     if (suggestion_rejected_)
       return;
 
     // TODO(beng): it'd be nice if we persisted some history/scoring here.
     for (const auto& name : app_names_) {
       if (base::StartsWith(name, new_contents,
                            base::CompareCase::INSENSITIVE_ASCII)) {
         base::string16 suffix = name;
         base::ReplaceSubstringsAfterOffset(&suffix, 0, new_contents,
                                            base::string16());
-        gfx::Range range(new_contents.size(), name.size());
+        gfx::Range range(static_cast<uint32_t>(new_contents.size()),
+                         static_cast<uint32_t>(name.size()));
         prompt_->SetText(name);
         prompt_->SelectRange(range);
         break;
       }
     }
   }
 
   std::string Canonicalize(const base::string16& input) const {
     base::string16 working;
     base::TrimWhitespace(input, base::TRIM_ALL, &working);
@@ skipping 44 matching lines @@
       gfx::Rect(10, 640, 0, 0));
   window->Show();
 }
 
 bool QuickLaunchApplication::AcceptConnection(shell::Connection* connection) {
   return true;
 }
 
 }  // namespace quick_launch
 }  // namespace mash