Don't attempt to forward declare StringPiece.

chrome/common/jstemplate_builder.h

 // Copyright (c) 2006-2008 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.
 
 // This provides some helper methods for building and rendering an
 // internal html page.  The flow is as follows:
 // - instantiate a builder given a webframe that we're going to render content
 //   into
 // - load the template html and load the jstemplate javascript into the frame
 // - given a json data object, run the jstemplate javascript which fills in
 //   template values
 
 #ifndef CHROME_COMMON_JSTEMPLATE_BUILDER_H_
 #define CHROME_COMMON_JSTEMPLATE_BUILDER_H_
 #pragma once
 
 #include <string>
 
+#include "base/string_piece.h"
+
 namespace base {
 class DictionaryValue;
-class StringPiece;
 }
 
 namespace jstemplate_builder {
 
 // A helper function that generates a string of HTML to be loaded.  The
 // string includes the HTML and the javascript code necessary to generate the
 // full page with support for JsTemplates.
 std::string GetTemplateHtml(const base::StringPiece& html_template,
                             const base::DictionaryValue* json,
                             const base::StringPiece& template_id);
@@ skipping 33 matching lines @@
 // Appends the source for i18n Templates in a script tag.
 void AppendI18nTemplateSourceHtml(std::string* output);
 
 // Appends the code that processes the i18n Template with the JSON. You
 // should call AppendJsTemplateSourceHtml and AppendJsonHtml before calling
 // this.
 void AppendI18nTemplateProcessHtml(std::string* output);
 
 }  // namespace jstemplate_builder
 #endif  // CHROME_COMMON_JSTEMPLATE_BUILDER_H_