[iOS] Stop injecting __gCrWeb['windowId'].

Every frame creates a frameId in JavaScript which can be used to
uniquely identify the main frame. Thus the generation and injection of a
windowID is no longer necessary.

Bug: 905939
Change-Id: Icef30a79a1d87bb455e4fb9b2403df74ec5b47b9
Reviewed-on: https://chromium-review.googlesource.com/c/1365410
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616613}
12 files changed