Don't check URLs against Safe Browsing if not supported.

chrome/browser/safe_browsing/database_manager.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.
 //
 // The Safe Browsing service is responsible for downloading anti-phishing and
 // anti-malware tables and checking urls against them.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_DATABASE_MANAGER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_DATABASE_MANAGER_H_
 
@@ skipping 25 matching lines @@
 
     // Called when the result of checking a download URL is known.
     virtual void OnCheckDownloadUrlResult(const std::vector<GURL>& url_chain,
                                           SBThreatType threat_type) {}
 
     // Called when the result of checking a set of extensions is known.
     virtual void OnCheckExtensionsResult(
         const std::set<std::string>& threats) {}
   };
 
+  // Returns true if URL-checking is supported on this build+device.
+  // If false, calls to CheckBrowseUrl may dcheck-fail.
+  virtual bool IsSupported() const = 0;
+
   // Returns true if the url's scheme can be checked.
   virtual bool CanCheckUrl(const GURL& url) const = 0;
 
   // Returns whether download protection is enabled.
   virtual bool download_protection_enabled() const = 0;
 
   // Called on the IO thread to check if the given url is safe or not.  If we
   // can synchronously determine that the url is safe, CheckUrl returns true.
   // Otherwise it returns false, and "client" is called asynchronously with the
   // result when it is ready.
@@ skipping 58 matching lines @@
   // on IO thread. If shutdown is true, the manager is disabled permanently.
   virtual void StopOnIOThread(bool shutdown) = 0;
 
  protected:
   virtual ~SafeBrowsingDatabaseManager() {}
 
   friend class base::RefCountedThreadSafe<SafeBrowsingDatabaseManager>;
 };  // class SafeBrowsingDatabaseManager
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_DATABASE_MANAGER_H_