[refactor] - More cases of casts to WebFrameWidget replaced by GetFrameWidget()

This conitnues the refactor in
https://chromium-review.googlesource.com/q/I940f44aeb5af65f4b8cac9bf4fa593d52319d5c9.

Bug: 669219
Change-Id: I4a828d1534cce44d2d60eb5069e9aee9b0f5b89f
Reviewed-on: https://chromium-review.googlesource.com/876482
Reviewed-by: Alex Moshchuk <[email protected]>
Commit-Queue: Ehsan Karamad <[email protected]>
Cr-Commit-Position: refs/heads/master@{#530705}
1 file changed