GitLab

- Enabled/implemented IsOffscreen property for UIA in
AXPlatformNodeWin::GetPropertyValue and assoicated browser tests.
GetPropertyValue calculates isOffscreen status by utilizing
AXTree::RelativeToTreeBounds, which looks at the bounds of the
node relative to its ancestor and rootWebArea bounds to determine
the isOffscreen status.

- Modified AccessibilityWinBrowserTests::FindNodeInSubtree to take
into account of StringAttribute::kValue when finding the node.

Bug: 844149
Change-Id: Ied62e00814957a6ca97b1849935ec692f1acf03a
Reviewed-on: https://chromium-review.googlesource.com/c/1481800
Commit-Queue: Victor Fei <vicfei@microsoft.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636934}