Check for NULL NativeView in linux/mac Screen::GetDisplayNearestWindow().

Check for NULL NativeView in linux/mac Screen::GetDisplayNearestWindow().

This is similar to what ScreenAsh::GetDisplayNearestWindow() is doing.
There can be cases when NativeView is NULL.

BUG=419611
Test=See bug description.

Committed: https://crrev.com/7b68c34c60f3f4b26245bc74ff6f4376699ef8cc
Cr-Commit-Position: refs/heads/master@{#297883}

[lazyboy, 2014-10-02 03:37:22]

lazyboy@chromium.org changed reviewers:
+ sky@chromium.org

[lazyboy, 2014-10-02 03:37:22]

Hi Scott,
This CL is not necessary to fix http://crbug.com/419611, but I felt this would
be a good change to make.
Thanks.

[sky, 2014-10-02 15:56:17]

I think this is ok, but you should clear up in screen.h what NULL means.

[lazyboy, 2014-10-02 16:16:21]

https://chromiumcodereview.appspot.com/618413002/diff/20001/ui/gfx/screen.h
File ui/gfx/screen.h (right):

https://chromiumcodereview.appspot.com/618413002/diff/20001/ui/gfx/screen.h#n...
ui/gfx/screen.h:74: // If the window is NULL or the window is not rooted to a
display this will
I've added this comment, if that's what you meant.

[sky, 2014-10-02 17:23:58]

LGTM

[lazyboy, 2014-10-02 19:45:05]

The CQ bit was checked by lazyboy@chromium.org

[commit-bot: I haz the power, 2014-10-02 19:45:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/618413002/20001

[commit-bot: I haz the power, 2014-10-02 19:51:29]

Committed patchset #2 (id:20001) as 01112f6811d23cbfb5398309290d26bd5593d0d3

[commit-bot: I haz the power, 2014-10-02 19:52:01]

Patchset 2 (id:??) landed as
https://crrev.com/7b68c34c60f3f4b26245bc74ff6f4376699ef8cc
Cr-Commit-Position: refs/heads/master@{#297883}