MSAA accParent of document should not be null.

It is important for get_accParent on the root of a document to return
the ROLE_SYSTEM_WINDOW object as it used to. This allows oleacc.lib's
WindowFromAccessibleObject implementation to work correctly.

Bug: 773208
Change-Id: I7c3ffd3968f7c48bdf6b94bf08dcdf849f4c763f
Reviewed-on: https://chromium-review.googlesource.com/754129
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Doug Turner <dougt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514417}
4 files changed