Remove traces of ShouldBlockRequestForFrame method

ShouldBlockRequestForFrame method of URLBlacklistManager was removed a
long time ago, but its definition persists. However, it's not needed and
therefore should be removed.

Change-Id: If2654066256afd35c90b0bf0e1b4d3615356b193
Reviewed-on: https://chromium-review.googlesource.com/c/1436051Reviewed-by: Pavol Marko <pmarko@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Oleg Davydov <burunduk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626499}

components/policy/core/browser/url_blacklist_manager.h

@@ -132,17 +132,6 @@ class POLICY_EXPORT URLBlacklistManager {
 
   URLBlacklist::URLBlacklistState GetURLBlacklistState(const GURL& url) const;
 
-  // Returns true if a request for |url| is blocked by the current blacklist.
-  //
-  // Should only be called for requests for frames (Main frames or subframes).
-  // Other subresources or background downloads (e.g. extensions updates, sync,
-  // etc) should not be filtered. The sync signin page will also not be
-  // filtered.
-  //
-  // |reason| is populated with the exact reason for blocking the url if and
-  // only if the return value is true otherwise it is left untouched.
-  bool ShouldBlockRequestForFrame(const GURL& url, int* reason) const;
-
   // Replaces the current blacklist.
   // Virtual for testing.
   virtual void SetBlacklist(std::unique_ptr<URLBlacklist> blacklist);