Switch Safe Browsing's metadata from string to struct.

chrome/browser/renderer_host/safe_browsing_resource_throttle.h

Index: chrome/browser/renderer_host/safe_browsing_resource_throttle.h
diff --git a/chrome/browser/renderer_host/safe_browsing_resource_throttle.h b/chrome/browser/renderer_host/safe_browsing_resource_throttle.h
index c363f7d48549d9c0c6061ada24184df872131a57..3589010a6bb1032c09ee758f2d0218602473f956 100644
--- a/chrome/browser/renderer_host/safe_browsing_resource_throttle.h
+++ b/chrome/browser/renderer_host/safe_browsing_resource_throttle.h
@@ -82,9 +82,10 @@ class SafeBrowsingResourceThrottle
   const char* GetNameForLogging() const override;
 
   // SafeBrowsingDabaseManager::Client implementation (called on IO thread):
-  void OnCheckBrowseUrlResult(const GURL& url,
-                              safe_browsing::SBThreatType result,
-                              const std::string& metadata) override;
+  void OnCheckBrowseUrlResult(
+      const GURL& url,
+      safe_browsing::SBThreatType result,
+      const safe_browsing::ThreatMetadata& metadata) override;
 
  protected:
   SafeBrowsingResourceThrottle(const net::URLRequest* request,