Add UseNotificationCompatBuilder feature flag

This flag enables the use of NotificationCompat.Builder on Android to
build web notifications instead of Notification.Builder. Also adds an
entry to chrome://flags and passes it down to Java so we can use it.

Bug: 697104
Change-Id: I41250ede6a1ca1978827c6641ea503098d19c8b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2740921
Reviewed-by: Peter Beverloo <[email protected]>
Reviewed-by: Ella Ge <[email protected]>
Commit-Queue: Richard Knoll <[email protected]>
Cr-Commit-Position: refs/heads/master@{#861959}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index d220d0c9..1b680c8 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -3348,6 +3348,12 @@
 const char kUpdateMenuTypeInlineUpdateInstallFailed[] =
     "Inline Update Error: Install Failed";
 
+const char kUseNotificationCompatBuilderName[] =
+    "Use NotificationCompat.Builder for Web Notifications";
+const char kUseNotificationCompatBuilderDescription[] =
+    "This enables using NotificationCompat.Builder instead of "
+    "Notification.Builder to create Web Notifications.";
+
 const char kUserMediaScreenCapturingName[] = "Screen Capture API";
 const char kUserMediaScreenCapturingDescription[] =
     "Allows sites to request a video stream of your screen.";