GitLab

Add an empty BridgedNativeWidgetHost interface and a largely-empty
BridgedNativeWidgetHostImpl implementation. These will be the browser
process part of BridgedNativeWidget.

Update NativeWidgetMac to have a BridgedNativeWidgetHost instead of a
BridgedNativeWidget, but still allow calls through the old interface.

The next steps will be a long process of shuffling members and methods
to these interfaces.

Bug: 859152
Change-Id: Id8be908302a32e52dc0ae1bf54fe19a285adccef
Reviewed-on: https://chromium-review.googlesource.com/1162875Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581146}