Revert of Change HistoryService::QueryURL to use CancelableTaskTracker

chrome/browser/history/history_backend.cc

Index: chrome/browser/history/history_backend.cc
diff --git a/chrome/browser/history/history_backend.cc b/chrome/browser/history/history_backend.cc
index b2c0c69d47316b07f3748b8b4663814d6475321e..a3fb38f409a0820f40588c851b7b4924b3cd26af 100644
--- a/chrome/browser/history/history_backend.cc
+++ b/chrome/browser/history/history_backend.cc
@@ -152,14 +152,6 @@
   scoped_refptr<HistoryBackend> history_backend_;
 };
 
-// HistoryBackend::QueryURLResult ----------------------------------------------
-
-HistoryBackend::QueryURLResult::QueryURLResult() : success(false) {
-}
-
-HistoryBackend::QueryURLResult::~QueryURLResult() {
-}
-
 // HistoryBackend --------------------------------------------------------------
 
 HistoryBackend::HistoryBackend(const base::FilePath& history_dir,
@@ -996,15 +988,26 @@
   return false;
 }
 
-HistoryBackend::QueryURLResult HistoryBackend::QueryURL(const GURL& url,
-                                                        bool want_visits) {
-  QueryURLResult result;
-  result.success = db_ && db_->GetRowForURL(url, &result.row);
-  // Optionally query the visits.
-  if (result.success && want_visits) {
-    db_->GetVisitsForURL(result.row.id(), &result.visits);
-  }
-  return result;
+void HistoryBackend::QueryURL(scoped_refptr<QueryURLRequest> request,
+                              const GURL& url,
+                              bool want_visits) {
+  if (request->canceled())
+    return;
+
+  bool success = false;
+  URLRow* row = &request->value.a;
+  VisitVector* visits = &request->value.b;
+  if (db_) {
+    if (db_->GetRowForURL(url, row)) {
+      // Have a row.
+      success = true;
+
+      // Optionally query the visits.
+      if (want_visits)
+        db_->GetVisitsForURL(row->id(), visits);
+    }
+  }
+  request->ForwardResult(request->handle(), success, row, visits);
 }
 
 TypedUrlSyncableService* HistoryBackend::GetTypedUrlSyncableService() const {