The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0c58c53be04ebddc41cee5d5088a5044639c6be6

commit 0c58c53be04ebddc41cee5d5088a5044639c6be6
Author: Kevin Marshall <kmarshall@chromium.org>
Date: Fri Nov 09 22:21:24 2018

Fuchsia: Always attach WebContentsObserver to a Frame's WebContents.

Currently, a Frame doesn't process WebContentsObserver methods until
a FIDL NavigationEventObserver is registered. WebContentsObserver is
useful for more than just navigation events, though! In cases where a
Frame is created but never passed a N.E.O., observer events like
ReadyToCommitNavigation() were not being received, which interfered
with on-load script injection.

This CL fixes the issue by attaching the observer at Frame
creation time.

Bug:  903880 
Change-Id: Ie3ab194fbaa60a5e18a4150be3ce4c6f7345845f
Reviewed-on: https://chromium-review.googlesource.com/c/1328147
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606997}
[modify] https://crrev.com/0c58c53be04ebddc41cee5d5088a5044639c6be6/webrunner/browser/frame_impl.cc
[modify] https://crrev.com/0c58c53be04ebddc41cee5d5088a5044639c6be6/webrunner/browser/frame_impl.h