Disable the Notification JavaScript constructor for Android.

Android won't be able to support this reliably, and hasn't yet shipped this
feature, so this is the time to take it out.

This is part of a two-sided patch:
    [1] https://codereview.chromium.org/901843006
    [2] This patch.

BUG=441828

Review URL: https://codereview.chromium.org/920153002

Cr-Commit-Position: refs/heads/master@{#316572}

content/child/runtime_features.cc

@@ -64,6 +64,9 @@ static void SetRuntimeFeatureDefaultsForPlatform() {
   // the feature via experimental web platform features.
   if (base::FieldTrialList::FindFullName("NavigationTransitions") == "Enabled")
     WebRuntimeFeatures::enableNavigationTransitions(true);
+  // Android won't be able to reliably support non-persistent notifications, the
+  // intended behavior for which is in flux by itself.
+  WebRuntimeFeatures::enableNotificationConstructor(false);
 #else
   WebRuntimeFeatures::enableNavigatorContentUtils(true);
 #endif  // defined(OS_ANDROID)