Use MSAA_Role directly from BrowserAccessibility.

During the move of get_accRole(), I left the ia_role initialization in
BrowserAccessibilityComWin::InitRoleAndState(). This CL removes this
duplication and prevents any further drift between the files.

BUG=703369

Review-Url: https://codereview.chromium.org/2967493005
Cr-Commit-Position: refs/heads/master@{#485704}
6 files changed