Disable app_banner_manager_browsertest.cc. Systemic flakiness.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index de8bf2be193fa0e7145234974c2696ab27249884..ac30bdcc20c7fdfd69dab671c6b7f33aa29c58d0 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -1312,7 +1312,10 @@ test("browser_tests") {
       "../browser/autofill/autofill_server_browsertest.cc",
       "../browser/autofill/content_autofill_driver_browsertest.cc",
       "../browser/autofill/form_structure_browsertest.cc",
-      "../browser/banners/app_banner_manager_browsertest.cc",
+
+      # Disabled. Systemic flakiness. See http://crbug.com/660798.
+      # "../browser/banners/app_banner_manager_browsertest.cc",
+
       "../browser/bitmap_fetcher/bitmap_fetcher_browsertest.cc",
       "../browser/browser_encoding_browsertest.cc",
       "../browser/browsing_data/autofill_counter_browsertest.cc",