Stop going through WebView to set debug flags on the compositor

Instead of going through WebView (which may or may not have a main
frame being composited), go through the client of the frame's
WebFrameWidget.

For each debug property:
1. Move the API from WebLayerTreeView to WebWidgetClient
2. Have inspector go through the WebFrameWidget's client instead of
through WebView (and WebLayerTreeView).

Also removes the WebSetting for these, which were not used before this
CL.

R=avi@chromium.org, enne@chromium.org, pdr@chromium.org

Change-Id: I7c615878fe7f481d589548470d3c8878cf0b36e9
Bug: 912193
Reviewed-on: https://chromium-review.googlesource.com/c/1407438
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: enne <enne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623417}
13 files changed