AX_ROLE_HORIZONTAL_RULE is not required.

There is already SeparatorRole defined in blink, so better to remove HorizontalRuleRole from blink and return SeparatorRole for hr tag.
This patch makes the changes in chromium side.

This CL would be followed by one blink CL which will remove the defined redundant role in blink side and one chromium CL after that to enable AX test and exposing correctly on MAC platform.

BUG=384723

Review URL: https://codereview.chromium.org/709523002

Cr-Commit-Position: refs/heads/master@{#303364}
10 files changed