Ensure the keyboard is always shown when there are no suggestions.

This change addresses the case where an empty suggestions list is
received, following a very rich suggestions list from previous
Omnibox interaction.

Mediator's internal logic clears up the locally stored
AutocompleteResult as user completes interaction with the Omnibox,
making the subsequently received empty list detected as a no-op.

Bug: 1107562
Change-Id: Ifa50c9aea78e730a0424af411ea5d08c7dd5b015
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308134
Commit-Queue: Ender <ender@google.com>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790218}

chrome/android/java/src/org/chromium/chrome/browser/omnibox/suggestions/DropdownItemViewInfoListBuilder.java

@@ -206,6 +206,7 @@ class DropdownItemViewInfoListBuilder {
             mImageFetcher.clear();
         }
 
+        mBuiltListHasFullyConcealedElements = false;
         mHeaderProcessor.onUrlFocusChange(hasFocus);
         for (int index = 0; index < mPriorityOrderedSuggestionProcessors.size(); index++) {
             mPriorityOrderedSuggestionProcessors.get(index).onUrlFocusChange(hasFocus);