Don't trigger Overlay.nodeHighlightRequested if the hovered element is the same

We already store the last hovered node in SearchingForNodeTool so we can skip
sending duplicate Overlay.nodeHighlightRequested events if the hovered node
does not change.

Bug: 1169020
Change-Id: Id112e22127ec04d57695ab82a0bd4d41eb51793d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2640408
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845994}

third_party/blink/renderer/core/inspector/inspect_tools.cc

@@ -236,6 +236,7 @@ bool SearchingForNodeTool::HandleMouseMove(const WebMouseEvent& event) {
   }
 
   // Store values for the highlight.
+  bool hovered_node_changed = node != hovered_node_;
   hovered_node_ = node;
   event_target_node_ = (event.GetModifiers() & WebInputEvent::kShiftKey)
                            ? HoveredNodeForEvent(frame, event, false)
@@ -246,7 +247,8 @@ bool SearchingForNodeTool::HandleMouseMove(const WebMouseEvent& event) {
                   (WebInputEvent::kControlKey | WebInputEvent::kMetaKey);
 
   contrast_info_ = FetchContrast(node);
-  NodeHighlightRequested(node);
+  if (hovered_node_changed)
+    NodeHighlightRequested(node);
   return true;
 }
 

third_party/blink/web_tests/inspector-protocol/dom/dom-setInspectModeEnabled-expected.txt

 Tests inspect mode.
 DOM.inspectNodeRequested: div
+Number of nodeHighlightRequested events: 1
+Overlay.nodeHighlightRequested: div
 

third_party/blink/web_tests/inspector-protocol/dom/dom-setInspectModeEnabled.js

@@ -12,6 +12,9 @@
     testRunner.die(message.error.message);
     return;
   }
+  const highlightRequests = [];
+  dp.Overlay.onNodeHighlightRequested(event => highlightRequests.push(event));
+  dp.Input.dispatchMouseEvent({type: 'mouseMoved', button: 'left', buttons: 0, clickCount: 1, x: 175, y: 175 });
   dp.Input.dispatchMouseEvent({type: 'mouseMoved', button: 'left', buttons: 0, clickCount: 1, x: 150, y: 150 });
   dp.Input.dispatchMouseEvent({type: 'mousePressed', button: 'left', buttons: 0, clickCount: 1, x: 150, y: 150 });
   dp.Input.dispatchMouseEvent({type: 'mouseReleased', button: 'left', buttons: 1, clickCount: 1, x: 150, y: 150 });
@@ -19,6 +22,8 @@
   var message = await dp.Overlay.onceInspectNodeRequested();
   message = await dp.DOM.pushNodesByBackendIdsToFrontend({backendNodeIds: [message.params.backendNodeId]});
   testRunner.log('DOM.inspectNodeRequested: ' + nodeTracker.nodeForId(message.result.nodeIds[0]).localName);
+  testRunner.log('Number of nodeHighlightRequested events: ' + highlightRequests.length);
+  testRunner.log('Overlay.nodeHighlightRequested: ' + nodeTracker.nodeForId(highlightRequests[0].params.nodeId).localName);
   testRunner.completeTest();
 })