Implement support for ARIA code, strong, emphasis, and time roles

* Create ax::mojom::Role::kCode, kEmphasis, and kStrong
* Map to accessibility APIs as defined in Core-AAM specification

Because it is up to content authors and toolkits/frameworks to
style these roles as they see fit, font and format information
will be exposed based on authoring. We cannot assume (and thus
should not automatically expose) bold for the strong role or
italics for the emphasis role.

Bug: 1017195
Change-Id: I4fa6d300de27b01abd6c72742c4cf1ac90f63c01
Reviewed-by: Dominic Mazzoni <>
Reviewed-by: Kevin Babbitt <>
Reviewed-by: Daniel Cheng <>
Reviewed-by: Aaron Leventhal <>
Commit-Queue: Joanmarie Diggs <>
Cr-Commit-Position: refs/heads/master@{#709986}
45 files changed