Switch Safe Browsing's metadata from string to struct.

components/safe_browsing_db/safe_browsing_api_handler.h

 // Copyright 2015 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.
 //
 // Glue to pass Safe Browsing API requests between
 // RemoteSafeBrowsingDatabaseManager and Java-based API to check URLs.
 
 #ifndef COMPONENTS_SAFE_BROWSING_DB_SAFE_BROWSING_API_HANDLER_H_
 #define COMPONENTS_SAFE_BROWSING_DB_SAFE_BROWSING_API_HANDLER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "components/safe_browsing_db/util.h"
 #include "url/gurl.h"
 
 namespace safe_browsing {
 
 class SafeBrowsingApiHandler {
  public:
   // Singleton interface.
   static void SetInstance(SafeBrowsingApiHandler* instance);
   static SafeBrowsingApiHandler* GetInstance();
 
   typedef base::Callback<void(SBThreatType sb_threat_type,
-                              const std::string& metadata)>
+                              const ThreatMetadata& metadata)>
+      URLCheckCallbackMeta;
+
+  // TODO(nparker): Remove this as part of crbug/589610.
+  typedef base::Callback<void(SBThreatType sb_threat_type,
+                              const std::string& metadata_str)>
       URLCheckCallback;
 
   // Makes Native->Java call and invokes callback when check is done.
+  // TODO(nparker): Switch this back to pure virtual. crbug/589610.
+  virtual void StartURLCheck(const URLCheckCallbackMeta& callback,
+                             const GURL& url,
+                             const std::vector<SBThreatType>& threat_types);
+
+  // TODO(nparker): Remove this as part of crbug/589610.
   virtual void StartURLCheck(const URLCheckCallback& callback,
                              const GURL& url,
-                             const std::vector<SBThreatType>& threat_types) = 0;
+                             const std::vector<SBThreatType>& threat_types) {};
 
   virtual ~SafeBrowsingApiHandler() {}
 
  private:
   // Pointer not owned.
   static SafeBrowsingApiHandler* instance_;
 };
 
 }  // namespace safe_browsing
 
 #endif  // COMPONENTS_SAFE_BROWSING_DB_SAFE_BROWSING_API_HANDLER_H_