Make various string_util functions take StringPieces instead of char[].

chrome/browser/guest_view/ad_view/ad_view_guest.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 "chrome/browser/guest_view/ad_view/ad_view_guest.h"
 
 #include "base/strings/string_util.h"
 #include "chrome/browser/guest_view/ad_view/ad_view_constants.h"
 #include "chrome/browser/guest_view/guest_view_constants.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 32 matching lines @@
 
 void AdViewGuest::DidFailProvisionalLoad(
     int64 frame_id,
     const base::string16& frame_unique_name,
     bool is_main_frame,
     const GURL& validated_url,
     int error_code,
     const base::string16& error_description,
     content::RenderViewHost* render_view_host) {
   // Translate the |error_code| into an error string.
-  std::string error_type;
-  base::RemoveChars(net::ErrorToString(error_code), "net::", &error_type);
+  std::string error_type(net::ErrorToString(error_code));
+  DCHECK(StartsWithASCII(error_type, "net::", true));
+  error_type.erase(0, 5);
 
   scoped_ptr<base::DictionaryValue> args(new base::DictionaryValue());
   args->SetBoolean(guestview::kIsTopLevel, is_main_frame);
   args->SetString(guestview::kUrl, validated_url.spec());
   args->SetString(guestview::kReason, error_type);
   DispatchEvent(new GuestViewBase::Event(adview::kEventLoadAbort, args.Pass()));
 }