[Extensions] Remove NOTIFICATION_EXTENSION_LOAD_ERROR from test files

The NotificationService is deprecated. Added a LoadErrorReporterWaiter
in //chrome to move WaitForExtensionLoadError from //extension to
//chrome to avoid dependencies from //chrome. Thus ChromeTestExtensionLoader
and ExtensionPolicyTest will instead call the waiter. Finished removing
all NOTIFICATION_EXTENSION_LOAD_ERROR, thus removed the load error from
NotificationType enum.

Bug: 1174731

Change-Id: I6c187ed4a1686e9624897b018e21a024a3d2f631
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2691578
Reviewed-by: Nicolas Ouellet-Payeur <[email protected]>
Reviewed-by: Devlin <[email protected]>
Commit-Queue: Emilia Paz <[email protected]>
Cr-Commit-Position: refs/heads/master@{#857770}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index d3bcf54..3179ae4 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -6905,6 +6905,8 @@
       "extensions/chrome_test_extension_loader.h",
       "extensions/extension_action_test_util.cc",
       "extensions/extension_action_test_util.h",
+      "extensions/load_error_waiter.cc",
+      "extensions/load_error_waiter.h",
       "extensions/mock_extension_special_storage_policy.cc",
       "extensions/mock_extension_special_storage_policy.h",
       "extensions/test_blocklist.cc",