Don't leak WebHistoryService::Request on HistoryService shutdown.

chrome/browser/history/history_service.h

Index: chrome/browser/history/history_service.h
diff --git a/chrome/browser/history/history_service.h b/chrome/browser/history/history_service.h
index cf061deab7a2ec9d345d5a5f96f2df688ed2a7bf..95d88a97a48a33948c76163416e6dde34decfe34 100644
--- a/chrome/browser/history/history_service.h
+++ b/chrome/browser/history/history_service.h
@@ -26,6 +26,7 @@
 #include "chrome/browser/history/delete_directive_handler.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/history/typed_url_syncable_service.h"
+#include "chrome/browser/history/web_history_service.h"
 #include "chrome/browser/search_engines/template_url_id.h"
 #include "chrome/common/ref_counted_util.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service.h"
@@ -816,6 +817,11 @@ class HistoryService : public CancelableRequestProvider,
   // specified priority. The task will have ownership taken.
   void ScheduleTask(SchedulePriority priority, const base::Closure& task);
 
+  // Cleans up after a WebHistoryService::Request completes.
+  void WebHistoryServiceRequestComplete(
+      history::WebHistoryService::Request* request,
+      bool success);
+
   // Schedule ------------------------------------------------------------------
   //
   // Functions for scheduling operations on the history thread that have a
@@ -1067,6 +1073,11 @@ class HistoryService : public CancelableRequestProvider,
 
   history::DeleteDirectiveHandler delete_directive_handler_;
 
+  // Maintain the set of pending WebHistoryService requests so they may all be
+  // cancelled on profile shutdown.
+  std::set<history::WebHistoryService::Request*>
+      pending_web_history_service_requests_;
+
   DISALLOW_COPY_AND_ASSIGN(HistoryService);
 };