Add asserts to TestingProfile::CreateHistoryService to ensure files are deleted

chrome/test/base/testing_profile.h

Index: chrome/test/base/testing_profile.h
diff --git a/chrome/test/base/testing_profile.h b/chrome/test/base/testing_profile.h
index 939e77231294105186c0533fa0b86432634ae330..91a2a22f0c6f217c06b9f07bf51bc6b2bfce2fca 100644
--- a/chrome/test/base/testing_profile.h
+++ b/chrome/test/base/testing_profile.h
@@ -132,8 +132,8 @@ class TestingProfile : public Profile {
   // deletes the directory containing the files used by HistoryService, this
   // only matters if you're recreating the HistoryService.  If |no_db| is true,
   // the history backend will fail to initialize its database; this is useful
-  // for testing error conditions.
-  void CreateHistoryService(bool delete_file, bool no_db);
+  // for testing error conditions. Returns true on success.
+  bool CreateHistoryService(bool delete_file, bool no_db) WARN_UNUSED_RESULT;
 
   // Shuts down and nulls out the reference to HistoryService.
   void DestroyHistoryService();