[Contextual Search] Add more node checks before triggering.

Now showUnhandledTapUIIfNeeded makes an additional check to see if it is appropriate to trigger: if the tapped node is an ARIA widget or not, according to the accessibility code in Blink.

This CL is dependent on a Blink CL: 885163002

BUG=451096

Review URL: https://codereview.chromium.org/868933002

Cr-Commit-Position: refs/heads/master@{#318275}

content/renderer/render_widget.cc

@@ -2181,7 +2181,8 @@ void RenderWidget::showUnhandledTapUIIfNeeded(
     bool page_changed) {
   DCHECK(handling_input_event_);
   bool should_trigger = !page_changed && tapped_node.isTextNode() &&
-                        !tapped_node.isContentEditable();
+                        !tapped_node.isContentEditable() &&
+                        !tapped_node.isInsideFocusableElementOrARIAWidget();
   if (should_trigger) {
     Send(new ViewHostMsg_ShowUnhandledTapUIIfNeeded(routing_id_,
         tapped_position.x, tapped_position.y));

content/renderer/render_widget.h

@@ -193,6 +193,8 @@ class CONTENT_EXPORT RenderWidget
 #if defined(OS_ANDROID)
   // Notifies that a tap was not consumed, so showing a UI for the unhandled
   // tap may be needed.
+  // Performs various checks on the given WebNode to apply heuristics to
+  // determine if triggering is appropriate.
   virtual void showUnhandledTapUIIfNeeded(
       const blink::WebPoint& tapped_position,
       const blink::WebNode& tapped_node,