Fix keyboard input stopping to work after tabbing through omnibox.

This change addresses problem where keyboard would cease to work on any
site (including google.com) for any user who tabs through the omnibox.

Affects Android 7.

Users tabbing through the omnibox would end up in a bizarre state, where
after leaving the Omnibox by pressing tab focus would be granted to the
Omnibox Suggestions Results list element. The list would next change
visibility, after which Android 7 seems to be taking to action (ie. not
looking for the next focusable element), redirecting all subsequent user
input to an invisible element.

Nearly all subsequent input is consumed by that invisible element - with
an exception of shift-tab, which brings focus back to the Omnibox (but
would offer no remedy).

The offered solution is to prevent FocusFinder from considering
OmniboxSuggestionsList elements as candidates when searching for next
focusable element.

Suggestion results continue to be focusable for talkback / a11y enabled
users.

Bug: 805718

Change-Id: I49fb6daefec2175c06d4631e2b805d758a082f24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1795319Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Ender <ender@google.com>
Cr-Commit-Position: refs/heads/master@{#695702}

chrome/android/java/res/layout/omnibox_results_container.xml

@@ -8,4 +8,5 @@
     android:visibility="gone"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
+    android:descendantFocusability="blocksDescendants"
     />