webui: Change slightly how the scale-factor gets parsed from a URL.

chrome/browser/ui/webui/web_ui_util.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_WEB_UI_UTIL_H_
 #define CHROME_BROWSER_UI_WEBUI_WEB_UI_UTIL_H_
 
 #include <string>
 
 #include "base/string_piece.h"
@@ skipping 20 matching lines @@
 // image. Returns empty string if a resource does not exist for given
 // |resource_id|.
 std::string GetImageDataUrlFromResource(int resource_id);
 
 // Extracts a disposition from click event arguments. |args| should contain
 // an integer button and booleans alt key, ctrl key, meta key, and shift key
 // (in that order), starting at |start_index|.
 WindowOpenDisposition GetDispositionFromClick(const ListValue* args,
                                               int start_index);
 
-// Given a scale factor such as "1x" or "2x" returns the ScaleFactor enum
-// value for this scale factor.
-ui::ScaleFactor ParseScaleFactor(const base::StringPiece& identifier);
+// Given a scale factor such as "1x" or "2x", sets |scale_factor| to the
+// ScaleFactor enum value for this scale factor. If the scale factor could not
+// be determined correctly from the string, then |scale_factor| is set to
+// SCALE_FACTOR_NONE, and false is returned.
+bool ParseScaleFactor(const base::StringPiece& identifier,
+                      ui::ScaleFactor* scale_factor);
 
 // Parses a URL containing some path @{scale}x. If it does not contain a scale
 // factor then the default scale factor is returned.
 void ParsePathAndScale(const GURL& url,
                        std::string* path,
                        ui::ScaleFactor* scale_factor);
 
 }  // namespace web_ui_util
 
 #endif  // CHROME_BROWSER_UI_WEBUI_WEB_UI_UTIL_H_