Fix broken mixed script Rappor metric and add browser test

chrome/renderer/content_settings_observer.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_RENDERER_CONTENT_SETTINGS_OBSERVER_H_
 #define CHROME_RENDERER_CONTENT_SETTINGS_OBSERVER_H_
 
 #include <map>
 #include <set>
 
@@ skipping 37 matching lines @@
   void SetContentSettingRules(
       const RendererContentSettingRules* content_setting_rules);
 
   bool IsPluginTemporarilyAllowed(const std::string& identifier);
 
   // Sends an IPC notification that the specified content type was blocked.
   void DidBlockContentType(ContentSettingsType settings_type);
 
   // Sends an IPC notification that the specified content type was blocked
   // with additional metadata.
+  //
+  // When |settings_type| is CONTENT_SETTINGS_TYPE_MIXEDSCRIPT, the
+  // browser process expects |details| to contain a valid GURL
+  // describing the mixed script that was run.
   void DidBlockContentType(ContentSettingsType settings_type,
                            const base::string16& details);
 
   // blink::WebContentSettingsClient implementation.
   bool allowDatabase(const blink::WebString& name,
                      const blink::WebString& display_name,
                      unsigned long estimated_size) override;
   void requestFileSystemAccessAsync(
       const blink::WebContentSettingCallbacks& callbacks) override;
   bool allowImage(bool enabled_per_settings,
@@ skipping 91 matching lines @@
   typedef std::map<int, blink::WebContentSettingCallbacks> PermissionRequestMap;
   PermissionRequestMap permission_requests_;
 
   // If true, IsWhitelistedForContentSettings will always return true.
   const bool should_whitelist_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSettingsObserver);
 };
 
 #endif  // CHROME_RENDERER_CONTENT_SETTINGS_OBSERVER_H_