Nasty hack to pick the right origin for a sheet above an app window.

In r546e2e6931 GetSheetParentBoundsForParentView was added to work around
the presense of dev tools in the view hierarchy when calculating the center
of the web contents view. In an app window there is no dev tools view so
this patch falls back to the parent view's normal bounds.

BUG=

Review URL: https://codereview.chromium.org/659823003

Cr-Commit-Position: refs/heads/master@{#299790}
1 file changed