Bug 1668134 - part 1: Make `nsPIDOMWindowInner` have an API to know whether the window or its descendants has had `beforeinput` event listeners r=smaug

When `HTMLEditor` instances are destroyed, I'd like to collect how much
instances are worked with `beforeinput` event listeners.  Before adding such
telemetry probe, this patch adds methods to set/get whether a `beforeinput`
event listener has had added or not to `nsPIDOMWindowInner`.

Differential Revision: https://phabricator.services.mozilla.com/D92546

dom/base/nsGlobalWindowInner.cpp

@@ -7479,6 +7479,7 @@ nsPIDOMWindowInner::nsPIDOMWindowInner(nsPIDOMWindowOuter* aOuterWindow,
       mMayHaveSelectionChangeEventListener(false),
       mMayHaveMouseEnterLeaveEventListener(false),
       mMayHavePointerEnterLeaveEventListener(false),
+      mMayHaveBeforeInputEventListenerForTelemetry(false),
       mOuterWindow(aOuterWindow),
       mWindowID(0),
       mHasNotifiedGlobalCreated(false),

dom/base/nsPIDOMWindow.h

@@ -224,6 +224,24 @@ class nsPIDOMWindowInner : public mozIDOMWindow {
     mMayHavePointerEnterLeaveEventListener = true;
   }
 
+  /**
+   * Call this to check whether some node (this window, its document,
+   * or content in that document) has a beforeinput event listener.
+   * Returing false may be wrong if some nodes have come from another document
+   * with `Document.adoptNode`.
+   */
+  bool HasBeforeInputEventListenersForTelemetry() const {
+    return mMayHaveBeforeInputEventListenerForTelemetry;
+  }
+
+  /**
+   * Call this to indicate that some node (this window, its document,
+   * or content in that document) has a beforeinput event listener.
+   */
+  void SetHasBeforeInputEventListenersForTelemetry() {
+    mMayHaveBeforeInputEventListenerForTelemetry = true;
+  }
+
   // Sets the event for window.event. Does NOT take ownership, so
   // the caller is responsible for clearing the event before the
   // event gets deallocated. Pass nullptr to set window.event to
@@ -588,6 +606,9 @@ class nsPIDOMWindowInner : public mozIDOMWindow {
   bool mMayHaveSelectionChangeEventListener;
   bool mMayHaveMouseEnterLeaveEventListener;
   bool mMayHavePointerEnterLeaveEventListener;
+  // Only used for telemetry probes.  This may be wrong if some nodes have
+  // come from another document with `Document.adoptNode`.
+  bool mMayHaveBeforeInputEventListenerForTelemetry;
 
   // Our inner window's outer window.
   nsCOMPtr<nsPIDOMWindowOuter> mOuterWindow;

dom/events/EventListenerManager.cpp

@@ -382,6 +382,10 @@ void EventListenerManager::AddEventListenerInternal(
         doc->SetUseCounter(eUseCounter_custom_onfinish);
       }
     }
+  } else if (aTypeAtom == nsGkAtoms::onbeforeinput) {
+    if (nsPIDOMWindowInner* window = GetInnerWindowForTarget()) {
+      window->SetHasBeforeInputEventListenersForTelemetry();
+    }
   }
 
   if (IsApzAwareListener(listener)) {

editor/libeditor/EditorBase.cpp

@@ -2483,7 +2483,7 @@ EditorBase::ComputeInsertedRange(const EditorDOMPointInText& aInsertedPoint,
   // The DOM was potentially modified during the transaction. This is possible
   // through mutation event listeners. That is, the node could've been removed
   // from the doc or otherwise modified.
-  if (!MaybeHasMutationEventListeners(
+  if (!MayHaveMutationEventListeners(
           NS_EVENT_BITS_MUTATION_CHARACTERDATAMODIFIED)) {
     EditorDOMPointInText endOfInsertion(
         aInsertedPoint.ContainerAsText(),

editor/libeditor/EditorBase.h

@@ -205,7 +205,7 @@ class EditorBase : public nsIEditor,
   }
 
   /**
-   * MaybeHasMutationEventListeners() returns true when the window may have
+   * MayHaveMutationEventListeners() returns true when the window may have
    * mutation event listeners.
    *
    * @param aMutationEventType  One or multiple of NS_EVENT_BITS_MUTATION_*.
@@ -213,7 +213,7 @@ class EditorBase : public nsIEditor,
    *                            and at least one of NS_EVENT_BITS_MUTATION_* is
    *                            set to the window or in debug build.
    */
-  bool MaybeHasMutationEventListeners(
+  bool MayHaveMutationEventListeners(
       uint32_t aMutationEventType = 0xFFFFFFFF) const {
     if (IsTextEditor()) {
       // DOM mutation event listeners cannot catch the changes of
@@ -232,6 +232,20 @@ class EditorBase : public nsIEditor,
 #endif  // #ifdef DEBUG #else
   }
 
+  /**
+   * MayHaveBeforeInputEventListenersForTelemetry() returns true when the
+   * window may have or have had one or more `beforeinput` event listeners.
+   * Note that this may return false even if there is a `beforeinput`.
+   * See nsPIDOMWindowInner::HasBeforeInputEventListenersForTelemetry()'s
+   * comment for the detail.
+   */
+  bool MayHaveBeforeInputEventListenersForTelemetry() const {
+    if (const nsPIDOMWindowInner* window = GetInnerWindow()) {
+      return window->HasBeforeInputEventListenersForTelemetry();
+    }
+    return false;
+  }
+
   PresShell* GetPresShell() const {
     return mDocument ? mDocument->GetPresShell() : nullptr;
   }

editor/libeditor/HTMLEditSubActionHandler.cpp

@@ -3785,7 +3785,7 @@ EditActionResult HTMLEditor::AutoDeleteRangesHandler::Run(
                 "invalid");
             return EditActionHandled(NS_ERROR_FAILURE);
           }
-          if (aHTMLEditor.MaybeHasMutationEventListeners(
+          if (aHTMLEditor.MayHaveMutationEventListeners(
                   NS_EVENT_BITS_MUTATION_SUBTREEMODIFIED |
                   NS_EVENT_BITS_MUTATION_NODEREMOVED |
                   NS_EVENT_BITS_MUTATION_NODEREMOVEDFROMDOCUMENT)) {
@@ -4241,7 +4241,7 @@ EditActionResult HTMLEditor::AutoDeleteRangesHandler::
         "failed");
     return EditActionResult(rv);
   }
-  if (aHTMLEditor.MaybeHasMutationEventListeners(
+  if (aHTMLEditor.MayHaveMutationEventListeners(
           NS_EVENT_BITS_MUTATION_NODEREMOVED |
           NS_EVENT_BITS_MUTATION_NODEREMOVEDFROMDOCUMENT |
           NS_EVENT_BITS_MUTATION_ATTRMODIFIED |
@@ -5871,7 +5871,7 @@ HTMLEditor::AutoDeleteRangesHandler::DeleteParentBlocksWithTransactionIfEmpty(
 
   // If we have mutation event listeners, the next point is now outside of
   // editing host or editing hos has been changed.
-  if (aHTMLEditor.MaybeHasMutationEventListeners(
+  if (aHTMLEditor.MayHaveMutationEventListeners(
           NS_EVENT_BITS_MUTATION_NODEREMOVED |
           NS_EVENT_BITS_MUTATION_NODEREMOVEDFROMDOCUMENT |
           NS_EVENT_BITS_MUTATION_SUBTREEMODIFIED)) {
@@ -6534,7 +6534,7 @@ HTMLEditor::DeleteTextAndNormalizeSurroundingWhiteSpaces(
           break;  // There is no more text which we need to delete.
         }
       }
-      if (MaybeHasMutationEventListeners(
+      if (MayHaveMutationEventListeners(
               NS_EVENT_BITS_MUTATION_CHARACTERDATAMODIFIED) &&
           (NS_WARN_IF(!trackingEndToDelete.IsSetAndValid()) ||
            NS_WARN_IF(!trackingEndToDelete.IsInTextNode()))) {
@@ -6547,7 +6547,7 @@ HTMLEditor::DeleteTextAndNormalizeSurroundingWhiteSpaces(
       // we should stop handling the deletion.
       startToDelete =
           EditorDOMPointInText::AtEndOf(*startToDelete.ContainerAsText());
-      if (MaybeHasMutationEventListeners(
+      if (MayHaveMutationEventListeners(
               NS_EVENT_BITS_MUTATION_CHARACTERDATAMODIFIED) &&
           NS_WARN_IF(!startToDelete.IsBefore(endToDelete))) {
         return Err(NS_ERROR_EDITOR_UNEXPECTED_DOM_TREE);
@@ -6574,7 +6574,7 @@ HTMLEditor::DeleteTextAndNormalizeSurroundingWhiteSpaces(
         if (normalizedWhiteSpacesInLastNode.IsEmpty()) {
           break;  // There is no more text which we need to delete.
         }
-        if (MaybeHasMutationEventListeners(
+        if (MayHaveMutationEventListeners(
                 NS_EVENT_BITS_MUTATION_CHARACTERDATAMODIFIED |
                 NS_EVENT_BITS_MUTATION_NODEREMOVED |
                 NS_EVENT_BITS_MUTATION_NODEREMOVEDFROMDOCUMENT |
@@ -7264,7 +7264,7 @@ MoveNodeResult HTMLEditor::MoveOneHardLineContents(
           NS_SUCCEEDED(rvIgnored),
           "HTMLEditor::DeleteNodeWithTransaction() failed, but ignored");
       result.MarkAsHandled();
-      if (MaybeHasMutationEventListeners()) {
+      if (MayHaveMutationEventListeners()) {
         // Mutation event listener may make `offset` value invalid with
         // removing some previous children while we call
         // `DeleteNodeWithTransaction()` so that we should adjust it here.
@@ -7351,7 +7351,7 @@ MoveNodeResult HTMLEditor::MoveNodeOrChildrenWithTransaction(
     NS_WARNING("HTMLEditor::DeleteNodeWithTransaction() failed");
     return MoveNodeResult(rv);
   }
-  if (MaybeHasMutationEventListeners()) {
+  if (MayHaveMutationEventListeners()) {
     // Mutation event listener may make `offset` value invalid with
     // removing some previous children while we call
     // `DeleteNodeWithTransaction()` so that we should adjust it here.

editor/libeditor/WSRunObject.cpp

@@ -1826,7 +1826,7 @@ nsresult WhiteSpaceVisibilityKeeper::
   }
 
   EditorDOMRange rangeToDelete(aRangeToDelete);
-  bool mayBecomeUnexpectedDOMTree = aHTMLEditor.MaybeHasMutationEventListeners(
+  bool mayBecomeUnexpectedDOMTree = aHTMLEditor.MayHaveMutationEventListeners(
       NS_EVENT_BITS_MUTATION_SUBTREEMODIFIED |
       NS_EVENT_BITS_MUTATION_NODEREMOVED |
       NS_EVENT_BITS_MUTATION_NODEREMOVEDFROMDOCUMENT |