GitLab

Adjust the z-order of the virtual keyboard to ensure that it does not overlap context menus.  Previously, the virtual keyboard was placed just below the cursor container.  Adding a test case to ensure that the virtual keyboard overlaps normal windows but not menus.

BUG=377180

Review URL: https://codereview.chromium.org/565373002

Cr-Commit-Position: refs/heads/master@{#295268}