DevTools: notify CSS agent before a DOM node is unbound, not after

CSS agent expects to use DOM node id, so notifying it after the
node has been unbound is too late.

Change-Id: I4dad85d2676ae29998a7a3b05a026768fad97e98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2328295Reviewed-by: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793257}

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

@@ -2220,12 +2220,11 @@ void InspectorCSSAgent::DidAddDocument(Document* document) {
 
 void InspectorCSSAgent::DidRemoveDocument(Document* document) {}
 
-void InspectorCSSAgent::DidRemoveDOMNode(Node* node) {
-  if (!node)
-    return;
+void InspectorCSSAgent::WillRemoveDOMNode(Node* node) {
+  DCHECK(node);
 
   int node_id = dom_agent_->BoundNodeId(node);
-  if (node_id)
+  DCHECK(node_id);
   node_id_to_forced_pseudo_state_.erase(node_id);
 
   NodeToInspectorStyleSheet::iterator it =

third_party/blink/renderer/core/inspector/inspector_css_agent.h

@@ -300,7 +300,7 @@ class CORE_EXPORT InspectorCSSAgent final
   // InspectorDOMAgent::DOMListener implementation
   void DidAddDocument(Document*) override;
   void DidRemoveDocument(Document*) override;
-  void DidRemoveDOMNode(Node*) override;
+  void WillRemoveDOMNode(Node*) override;
   void DidModifyDOMAttr(Element*) override;
 
   // InspectorStyleSheet::Listener implementation

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

@@ -331,9 +331,9 @@ void InspectorDOMAgent::Unbind(Node* node, NodeToIdMap* nodes_map) {
     }
   }
 
-  nodes_map->erase(node);
   if (dom_listener_)
-    dom_listener_->DidRemoveDOMNode(node);
+    dom_listener_->WillRemoveDOMNode(node);
+  nodes_map->erase(node);
 
   bool children_requested = children_requested_.Contains(id);
   if (children_requested) {

third_party/blink/renderer/core/inspector/inspector_dom_agent.h

@@ -76,7 +76,7 @@ class CORE_EXPORT InspectorDOMAgent final
     virtual ~DOMListener() = default;
     virtual void DidAddDocument(Document*) = 0;
     virtual void DidRemoveDocument(Document*) = 0;
-    virtual void DidRemoveDOMNode(Node*) = 0;
+    virtual void WillRemoveDOMNode(Node*) = 0;
     virtual void DidModifyDOMAttr(Element*) = 0;
   };