Added HistoryService::GetHistoryCount() and helper functions in components/history

components/history/core/browser/history_service.cc

Index: components/history/core/browser/history_service.cc
diff --git a/components/history/core/browser/history_service.cc b/components/history/core/browser/history_service.cc
index 28bdd51cdb5cca43617ab5ff20c9656477a6cd05..fafadfb240e70eb1f3e558f1ac06bb5f2c7f11c5 100644
--- a/components/history/core/browser/history_service.cc
+++ b/components/history/core/browser/history_service.cc
@@ -667,6 +667,20 @@ base::CancelableTaskTracker::TaskId HistoryService::QueryURL(
                  base::Owned(query_url_result)));
 }
 
+// Statistics ------------------------------------------------------------------
+
+base::CancelableTaskTracker::TaskId HistoryService::GetHistoryCount(
+    const GetHistoryCountCallback& callback,
+    base::CancelableTaskTracker* tracker) {
+  DCHECK(thread_) << "History service being called after cleanup";
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  return tracker->PostTaskAndReplyWithResult(
+      thread_->task_runner().get(), FROM_HERE,
+      base::Bind(&HistoryBackend::GetHistoryCount, history_backend_.get()),
+      callback);
+}
+
 // Downloads -------------------------------------------------------------------
 
 // Handle creation of a download by creating an entry in the history service's