Remove WebWidget::IsFrameWidget.

The WebWidget in a frame-based RenderWidget is always a WebFrameWidget
now.

The TextInputClientObserver checks if the WebWidget is a WebFrameWidget
when it is not null, but for a frame-based RenderWidget is always a
WebFrameWidget now when not null, and becomes null instead of a non-
WebFrameWidget when the main local frame is detached. So we can just
check (and return directly) the nullptr instead.

[email protected]

Bug: 419087
Change-Id: If0c3eea72a468d5d1b63cc8a5427c7a17880c59a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1783919
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Commit-Queue: danakj <[email protected]>
Cr-Commit-Position: refs/heads/master@{#693728}
8 files changed