Bug 1550031 - Part 2: Update mutation breakpoint data on DOM Node removal. r=jlast

Differential Revision: https://phabricator.services.mozilla.com/D40717

--HG--
extra : moz-landing-system : lando

devtools/server/actors/inspector/walker.js

@@ -188,6 +188,10 @@ const IMMEDIATE_MUTATIONS = [
   "frameLoad",
   "newRoot",
   "pseudoClassLock",
+
+  // These should be delivered right away in order to be sure that the
+  // fronts have not been removed due to other non-throttled mutations.
+  "mutationBreakpoints",
 ];
 
 const HIDDEN_CLASS = "__fx-devtools-hide-shortcut__";
@@ -301,8 +305,6 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
     this.onNodeRemoved[EXCLUDED_LISTENER] = true;
     this.onAttributeModified = this.onAttributeModified.bind(this);
     this.onAttributeModified[EXCLUDED_LISTENER] = true;
-    this.onNodeRemovedFromDocument = this.onNodeRemovedFromDocument.bind(this);
-    this.onNodeRemovedFromDocument[EXCLUDED_LISTENER] = true;
 
     this.onMutations = this.onMutations.bind(this);
     this.onSlotchange = this.onSlotchange.bind(this);
@@ -1958,7 +1960,14 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
       rawDoc,
       true /* createIfNeeded */
     );
-    const originalBpsForNode = this._breakpointInfoForNode(rawNode) || {};
+    let originalBpsForNode = this._breakpointInfoForNode(rawNode);
+
+    if (!bpsForNode && !originalBpsForNode) {
+      return;
+    }
+
+    bpsForNode = bpsForNode || {};
+    originalBpsForNode = originalBpsForNode || {};
 
     if (Object.values(bpsForNode).some(Boolean)) {
       docMutationBreakpoints.nodes.set(rawNode, bpsForNode);
@@ -1983,7 +1992,6 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
       docMutationBreakpoints.counts.attribute += 1;
     }
 
-    this._updateNodeMutationListeners(rawNode);
     this._updateDocumentMutationListeners(rawDoc);
 
     const actor = this.getNode(rawNode);
@@ -1996,30 +2004,6 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
     }
   },
 
-  /**
-   * Controls whether this DOM node has a listener attached.
-   *
-   * @param {Node} rawNode The DOM node.
-   */
-  _updateNodeMutationListeners(rawNode) {
-    const bpInfo = this._breakpointInfoForNode(rawNode);
-    if (bpInfo && (bpInfo.subtree || bpInfo.removal || bpInfo.attribute)) {
-      eventListenerService.addSystemEventListener(
-        rawNode,
-        "DOMNodeRemovedFromDocument",
-        this.onNodeRemovedFromDocument,
-        true /* capture */
-      );
-    } else {
-      eventListenerService.removeSystemEventListener(
-        rawNode,
-        "DOMNodeRemovedFromDocument",
-        this.onNodeRemovedFromDocument,
-        true /* capture */
-      );
-    }
-  },
-
   /**
    * Controls whether this DOM document has event listeners attached for
    * handling of DOM mutation breakpoints.
@@ -2050,7 +2034,8 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
 
     if (
       docMutationBreakpoints.counts.subtree > 0 ||
-      docMutationBreakpoints.counts.removal > 0
+      docMutationBreakpoints.counts.removal > 0 ||
+      docMutationBreakpoints.counts.attribute > 0
     ) {
       eventListenerService.addSystemEventListener(
         rawDoc,
@@ -2120,7 +2105,11 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
 
   onNodeRemoved: function(evt) {
     const mutationBpInfo = this._breakpointInfoForNode(evt.target);
-    if (mutationBpInfo && mutationBpInfo.removal) {
+    const hasNodeRemovalEvent = mutationBpInfo && mutationBpInfo.removal;
+
+    this._clearMutationBreakpointsFromSubtree(evt.target);
+
+    if (hasNodeRemovalEvent) {
       this._breakOnMutation("nodeRemoved");
     } else {
       this.onSubtreeModified(evt);
@@ -2145,12 +2134,19 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
     }
   },
 
-  onNodeRemovedFromDocument: function(evt) {
-    this._updateMutationBreakpointState(evt.target, {
-      subtree: false,
-      removal: false,
-      attribute: false,
-    });
+  _clearMutationBreakpointsFromSubtree: function(targetNode) {
+    const targetDoc = targetNode.ownerDocument || targetNode;
+    const docMutationBreakpoints = this._mutationBreakpointsForDoc(targetDoc);
+    if (!docMutationBreakpoints || docMutationBreakpoints.nodes.size === 0) {
+      // Bail early for performance. If the doc has no mutation BPs, there is
+      // no reason to iterate through the children looking for things to detach.
+      return;
+    }
+
+    const walker = this.getDocumentWalker(targetNode);
+    do {
+      this._updateMutationBreakpointState(walker.currentNode, null);
+    } while (walker.nextNode());
   },
 
   /**
@@ -2503,11 +2499,7 @@ var WalkerActor = protocol.ActorClassWithSpec(walkerSpec, {
     const mutationBps = this._mutationBreakpointsForDoc(doc);
     const nodes = mutationBps ? Array.from(mutationBps.nodes.keys()) : [];
     for (const node of nodes) {
-      this._updateMutationBreakpointState(node, {
-        subtree: false,
-        removal: false,
-        attribute: false,
-      });
+      this._updateMutationBreakpointState(node, null);
     }
 
     if (this.rootDoc === doc) {