Bug 1816312, try to avoid creating Range objects in some common cases when spellchecker is disabled for contentEditable, r=masayuki

This is not very optimimal, but tracking spellchecking state in DOM tree is tricky because of multiple contentEditables and possibility to set spellcheck true/false anywhere etc.
At least this helps with the testcase quite a bit.

Differential Revision: https://phabricator.services.mozilla.com/D169870

dom/base/Document.cpp

@@ -6217,22 +6217,23 @@ void Document::DeferredContentEditableCountChange(Element* aElement) {
 
       RefPtr<HTMLEditor> htmlEditor = docshell->GetHTMLEditor();
       if (htmlEditor) {
-        RefPtr<nsRange> range = nsRange::Create(aElement);
-        IgnoredErrorResult res;
-        range->SelectNode(*aElement, res);
-        if (res.Failed()) {
-          // The node might be detached from the document at this point,
-          // which would cause this call to fail.  In this case, we can
-          // safely ignore the contenteditable count change.
-          return;
-        }
-
         nsCOMPtr<nsIInlineSpellChecker> spellChecker;
         rv = htmlEditor->GetInlineSpellChecker(false,
                                                getter_AddRefs(spellChecker));
         NS_ENSURE_SUCCESS_VOID(rv);
 
-        if (spellChecker) {
+        if (spellChecker &&
+            aElement->InclusiveDescendantMayNeedSpellchecking(htmlEditor)) {
+          RefPtr<nsRange> range = nsRange::Create(aElement);
+          IgnoredErrorResult res;
+          range->SelectNode(*aElement, res);
+          if (res.Failed()) {
+            // The node might be detached from the document at this point,
+            // which would cause this call to fail.  In this case, we can
+            // safely ignore the contenteditable count change.
+            return;
+          }
+
           rv = spellChecker->SpellCheckRange(range);
           NS_ENSURE_SUCCESS_VOID(rv);
         }

dom/base/FragmentOrElement.cpp

@@ -22,6 +22,7 @@
 #include "mozilla/EventListenerManager.h"
 #include "mozilla/ElementAnimationData.h"
 #include "mozilla/HTMLEditor.h"
+#include "mozilla/mozInlineSpellChecker.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/RestyleManager.h"
 #include "mozilla/TextEditor.h"
@@ -356,6 +357,13 @@ void nsIContent::ConstructUbiNode(void* storage) {
   JS::ubi::Concrete<nsIContent>::construct(storage, this);
 }
 
+bool nsIContent::InclusiveDescendantMayNeedSpellchecking(HTMLEditor* aEditor) {
+  // Return true if the node may have elements as children, since those or their
+  // descendants may have spellcheck attributes.
+  return HasFlag(NODE_MAY_HAVE_ELEMENT_CHILDREN) ||
+         mozInlineSpellChecker::ShouldSpellCheckNode(aEditor, this);
+}
+
 //----------------------------------------------------------------------
 
 static inline JSObject* GetJSObjectChild(nsWrapperCache* aCache) {

dom/base/moz.build

@@ -565,6 +565,7 @@ LOCAL_INCLUDES += [
     "/dom/xml",
     "/dom/xslt/xpath",
     "/dom/xul",
+    "/extensions/spellcheck/src",
     "/gfx/2d",
     "/image",
     "/js/xpconnect/loader",

dom/base/nsIContent.h

@@ -17,6 +17,7 @@ class nsIFrame;
 
 namespace mozilla {
 class EventChainPreVisitor;
+class HTMLEditor;
 struct URLExtraData;
 namespace dom {
 struct BindContext;
@@ -624,6 +625,12 @@ class nsIContent : public nsINode {
     return rc == 0;
   }
 
+  /**
+   * Use this method with designMode and contentEditable to check if the
+   * node may need spellchecking.
+   */
+  bool InclusiveDescendantMayNeedSpellchecking(mozilla::HTMLEditor* aEditor);
+
  protected:
   /**
    * Lazily allocated extended slots to avoid

editor/libeditor/HTMLEditor.cpp

@@ -4423,12 +4423,26 @@ void HTMLEditor::DoContentInserted(nsIContent* aChild,
 
     // Update spellcheck for only the newly-inserted node (bug 743819)
     if (mInlineSpellChecker) {
-      RefPtr<nsRange> range = nsRange::Create(aChild);
       nsIContent* endContent = aChild;
       if (aInsertedOrAppended == eAppended) {
+        nsIContent* child = nullptr;
+        for (child = aChild; child; child = child->GetNextSibling()) {
+          if (child->InclusiveDescendantMayNeedSpellchecking(this)) {
+            break;
+          }
+        }
+        if (!child) {
+          // No child needed spellchecking, return.
+          return;
+        }
+
         // Maybe more than 1 child was appended.
         endContent = container->GetLastChild();
+      } else if (!aChild->InclusiveDescendantMayNeedSpellchecking(this)) {
+        return;
       }
+
+      RefPtr<nsRange> range = nsRange::Create(aChild);
       range->SelectNodesInContainer(container, aChild, endContent);
       DebugOnly<nsresult> rvIgnored =
           mInlineSpellChecker->SpellCheckRange(range);