Update screen reader with new Omnibox text

AX-Relnotes: Omnibox accessibility reliability
Bug: 943105, 1039422
Change-Id: Icf6adebabdcd7d9627c58f3c7260fc5359043fab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2226061
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Auto-Submit: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774400}

chrome/browser/ui/views/omnibox/omnibox_view_views.cc

@@ -826,11 +826,17 @@ void OmniboxViewViews::OnRevertTemporaryText(const base::string16& display_text,
   // TextChanged(), since OmniboxPopupModel::ResetToDefaultMatch() has already
   // been called by now, and it would've called TextChanged() if it was
   // warranted.
+  // However, it's important to notify accessibility that the value has changed,
+  // otherwise the screen reader will use the old accessibility label text.
+  NotifyAccessibilityEvent(ax::mojom::Event::kValueChanged, true);
 }
 
 void OmniboxViewViews::ClearAccessibilityLabel() {
+  if (friendly_suggestion_text_.empty())
+    return;
   friendly_suggestion_text_.clear();
   friendly_suggestion_text_prefix_length_ = 0;
+  NotifyAccessibilityEvent(ax::mojom::Event::kValueChanged, true);
 }
 
 void OmniboxViewViews::SetAccessibilityLabel(const base::string16& display_text,