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This change disables supports_multiple_windows by default to
Webview controller, in order to open new window navigations
in the current view.

Bug: b/170218696
Test: Sample website on Chromecast navigates on the current view.
Change-Id: I44cb7d7e9c8ffa42789f7019779fc9c87935ba92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2533679Reviewed-by: Sean Topping <seantopping@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Jiaqi Han <jiaqih@google.com>
Cr-Commit-Position: refs/heads/master@{#827432}