Make OnDataTimedout and OnDidPerformInstallableCheck mutually exclusive.

chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc

Index: chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc
diff --git a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc
index c8bfaf1bf4f3ad4f56063c92402ec05061852373..df56a43677e174441786283a5e50241bc5f869fb 100644
--- a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc
+++ b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher_unittest.cc
@@ -33,6 +33,9 @@
 #include "ui/gfx/image/image_unittest_util.h"
 #include "url/gurl.h"
 
+// TODO(zpeng): Effectively test scenarios where both timeout callback and
+// success callback are invoked. See crbug.com/697228.
+
 namespace {
 
 const char* kDefaultManifestUrl = "https://www.example.com/manifest.json";