Check for null return from GetNativeView().

Check for null return from GetNativeView().

At present many (all?) consumers of
RenderWidgetHostViewBase::GetNativeView() assume it always returns non-
null, but this may not be a safe assumption if the view is a
RenderWidgetHostViewChildFrame. This CL temporarily fixes a crash when
ChromeOS hits this case, while we review the behaviour of the consumers
of this function, and while we review the implementation in
RenderWidgetHostViewChildFrame.

BUG=644294, 644726
Review-Url: https://codereview.chromium.org/2322513002
Cr-Commit-Position: refs/heads/master@{#417288}
(cherry picked from commit 079861f265916d3b9d6323a2f4cf07cdba864a05)

Committed: https://chromium.googlesource.com/chromium/src/+/fd1a8a3acc82119847fd1ae38b50c84d34400c0d

[wjmaclean, 2016-09-12 14:23:04]

Description was changed from

==========
Check for null return from GetNativeView().

At present many (all?) consumers of
RenderWidgetHostViewBase::GetNativeView() assume it always returns non-
null, but this may not be a safe assumption if the view is a
RenderWidgetHostViewChildFrame. This CL temporarily fixes a crash when
ChromeOS hits this case, while we review the behaviour of the consumers
of this function, and while we review the implementation in
RenderWidgetHostViewChildFrame.

BUG=644294, 644726

Review-Url: https://codereview.chromium.org/2322513002
Cr-Commit-Position: refs/heads/master@{#417288}
(cherry picked from commit 079861f265916d3b9d6323a2f4cf07cdba864a05)
==========

to

==========
Check for null return from GetNativeView().

At present many (all?) consumers of
RenderWidgetHostViewBase::GetNativeView() assume it always returns non-
null, but this may not be a safe assumption if the view is a
RenderWidgetHostViewChildFrame. This CL temporarily fixes a crash when
ChromeOS hits this case, while we review the behaviour of the consumers
of this function, and while we review the implementation in
RenderWidgetHostViewChildFrame.

BUG=644294, 644726

Review-Url: https://codereview.chromium.org/2322513002
Cr-Commit-Position: refs/heads/master@{#417288}
(cherry picked from commit 079861f265916d3b9d6323a2f4cf07cdba864a05)

Committed:
https://chromium.googlesource.com/chromium/src/+/fd1a8a3acc82119847fd1ae38b50...
==========

[wjmaclean, 2016-09-12 14:23:06]

Committed patchset #1 (id:1) manually as
fd1a8a3acc82119847fd1ae38b50c84d34400c0d.