[Mfill Android] Allow autofill suggestions for empty fields

Currently, we hide the autofill UI when the focused field was cleared.
For the Autofill popup, hiding is correct. For the keyboard accessory,
there is no additional UI that would pop up so we want to show all
suggestions again.

Bug: 942492
Change-Id: Ia8507e8e6cfb4e93dff69e9c967a74218e691184
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1713517Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679998}

components/autofill/content/renderer/autofill_agent.cc

@@ -639,7 +639,8 @@ void AutofillAgent::ShowSuggestions(const WebFormControlElement& element,
   // criteria are not met.
   WebString value = element.EditingValue();
   if (value.length() > kMaxDataLength ||
-      (!options.autofill_on_empty_values && value.IsEmpty()) ||
+      (!IsKeyboardAccessoryEnabled() && !options.autofill_on_empty_values &&
+       value.IsEmpty()) ||
       (options.requires_caret_at_end &&
        (element.SelectionStart() != element.SelectionEnd() ||
         element.SelectionEnd() != static_cast<int>(value.length())))) {