Proactively preventing build break when https://bugs.webkit.org/show_bug.cgi?id=58456 lands.

chrome/renderer/extensions/extension_process_bindings.cc

 // Copyright (c) 2011 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/renderer/extensions/extension_process_bindings.h"
 
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 297 matching lines @@
   // Attach an event name to an object.
   static v8::Handle<v8::Value> GetLocalFileSystem(
       const v8::Arguments& args) {
     DCHECK(args.Length() == 2);
     DCHECK(args[0]->IsString());
     DCHECK(args[1]->IsString());
     std::string name(*v8::String::Utf8Value(args[0]));
     std::string path(*v8::String::Utf8Value(args[1]));
 
     WebFrame* webframe = WebFrame::frameForCurrentContext();
+#ifdef WEB_FILE_SYSTEM_TYPE_EXTERNAL
+    return webframe->createFileSystem(WebKit::WebFileSystem::TypeExternal,
+            WebKit::WebString::fromUTF8(name.c_str()),
+            WebKit::WebString::fromUTF8(path.c_str()));
+#else
     return webframe->createFileSystem(fileapi::kFileSystemTypeLocal,
             WebKit::WebString::fromUTF8(name.c_str()),
             WebKit::WebString::fromUTF8(path.c_str()));
+#endif
   }
 
   // Creates a new messaging channel to the tab with the given ID.
   static v8::Handle<v8::Value> OpenChannelToTab(const v8::Arguments& args) {
     // Get the current RenderView so that we can send a routed IPC message from
     // the correct source.
     RenderView* renderview = bindings_utils::GetRenderViewForCurrentContext();
     if (!renderview)
       return v8::Undefined();
 
@@ skipping 327 matching lines @@
     ExtensionProcessBindings::ThrowPermissionDeniedException(
       const std::string& function_name) {
   static const char kMessage[] =
       "You do not have permission to use '%s'. Be sure to declare"
       " in your manifest what permissions you need.";
   std::string error_msg = StringPrintf(kMessage, function_name.c_str());
 
   return v8::ThrowException(v8::Exception::Error(
       v8::String::New(error_msg.c_str())));
 }