Remove methods from BrowserAccessibilityComWin which aren't needed.

This is the first larger patch where we can start removing methods from
BrowserAccessibilityComWin that are completely implemented by
AXPlatformNodeWin.

Note, I believe the owner() check that is used in BrowserAccessibilityComWin
is not needed anymore. This is because the AXPlatformNodeWin should be
testing for a valid delegate in all of the exposed COM interfaces.

Also note, that I have removed changing the accessibility mode flags
from some of the unimplemented methods.  I do not believe that this will be
a problem since these methods aren't really used.

There will be a follow up that moves more over after we work out what
to do about handling of the mode flags.

BUG=703369

Review-Url: https://codereview.chromium.org/2981053002
Cr-Commit-Position: refs/heads/master@{#487738}
3 files changed