Cancel all pending Autocomplete operations on destroy.

Ensures that no suggestion updates are received after destroy() is called.

Bug: 1119805
Change-Id: I431fb60038274a8c6f54eb89d034822d77b08d09
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2373383Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Tomasz Wiszkowski <ender@google.com>
Cr-Commit-Position: refs/heads/master@{#801242}

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

@@ -194,6 +194,7 @@ class AutocompleteMediator implements OnSuggestionsReceivedListener, StartStopWi
     }
 
     public void destroy() {
+        stopAutocomplete(true);
         mDropdownViewInfoListBuilder.destroy();
         if (mTabObserver != null) {
             mTabObserver.destroy();