[omnibox] Handle tabbing to the tab switch button

Within the Omnibox suggestions pop-up list, the tab key will act like
a down arrow (and shift-tab, the up arrow), unless a suggestion is a
keyword suggestion, obviously. This change makes focus jump to the
tab switch button, if present, on tab key presses, before going on to
the next suggestion. Likewise, shift-tab is handled coming back up.
Finally, dragging also correctly changes the focus.

Bug: 780835
Change-Id: I3f33645ac36e0c03fa18267fb8bee9079b3cf297
Reviewed-on: https://chromium-review.googlesource.com/1014946
Commit-Queue: Kevin Bailey <[email protected]>
Reviewed-by: Justin Donnelly <[email protected]>
Cr-Commit-Position: refs/heads/master@{#554375}
9 files changed