[omnibox] Add name to icon for accessibility description

MacOS is capable of generating an accessibility description for the
search icon on the Omnibox, but we currently don't fill it in. This
CL adds a name to it (and there may be a follow-up to tweak the
"image" string that is also getting appended.)

Bug: 862745
Change-Id: I53f7250c848761127a29bdad4e215830c365bb97
Reviewed-on: https://chromium-review.googlesource.com/1138548
Reviewed-by: Justin Donnelly <[email protected]>
Commit-Queue: Kevin Bailey <[email protected]>
Cr-Commit-Position: refs/heads/master@{#576184}
2 files changed