Skip base::string16 if not necessary for WebString <-> ASCII conversion

content/child/simple_webmimeregistry_impl.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/child/simple_webmimeregistry_impl.h"
 
 #include "base/files/file_path.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/mime_util/mime_util.h"
 #include "media/base/mime_util.h"
 #include "media/filters/stream_parser_factory.h"
 #include "net/base/mime_util.h"
 #include "third_party/WebKit/public/platform/FilePathConversion.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 
 using blink::WebString;
 using blink::WebMimeRegistry;
 
 namespace content {
 
 // static
 std::string SimpleWebMimeRegistryImpl::ToASCIIOrEmpty(const WebString& string) {
-  return base::IsStringASCII(string)
-      ? base::UTF16ToASCII(base::StringPiece16(string))
-      : std::string();
+  return string.containsOnlyASCII() ? string.ascii() : std::string();
 }
 
 WebMimeRegistry::SupportsType SimpleWebMimeRegistryImpl::supportsMIMEType(
     const WebString& mime_type) {
   return mime_util::IsSupportedMimeType(ToASCIIOrEmpty(mime_type))
              ? WebMimeRegistry::IsSupported
              : WebMimeRegistry::IsNotSupported;
 }
 
 WebMimeRegistry::SupportsType SimpleWebMimeRegistryImpl::supportsImageMIMEType(
@@ skipping 63 matching lines @@
 
 WebString SimpleWebMimeRegistryImpl::wellKnownMimeTypeForExtension(
     const WebString& file_extension) {
   std::string mime_type;
   net::GetWellKnownMimeTypeFromExtension(
       blink::WebStringToFilePath(file_extension).value(), &mime_type);
   return WebString::fromUTF8(mime_type);
 }
 
 }  // namespace content