Bug 1832026, create TextControlState lazily, r=masayuki

Differential Revision: https://phabricator.services.mozilla.com/D195383

Author: Olli Pettay

dom/html/HTMLInputElement.cpp

@@ -1022,8 +1022,8 @@ HTMLInputElement::HTMLInputElement(already_AddRefed<dom::NodeInfo>&& aNodeInfo,
                 "Keep the size of HTMLInputElement under 512 to avoid "
                 "performance regression!");
 
-  // We are in a type=text so we now we currenty need a TextControlState.
-  mInputData.mState = TextControlState::Construct(this);
+  // We are in a type=text but we create TextControlState lazily.
+  mInputData.mState = nullptr;
 
   void* memory = mInputTypeMem;
   mInputType = InputType::Create(this, mType, memory);
@@ -1053,7 +1053,8 @@ void HTMLInputElement::FreeData() {
   if (!IsSingleLineTextControl(false)) {
     free(mInputData.mValue);
     mInputData.mValue = nullptr;
-  } else {
+  } else if (mInputData.mState) {
+    // XXX Passing nullptr to UnbindFromFrame doesn't do anything!
     UnbindFromFrame(nullptr);
     mInputData.mState->Destroy();
     mInputData.mState = nullptr;
@@ -1065,11 +1066,22 @@ void HTMLInputElement::FreeData() {
   }
 }
 
+void HTMLInputElement::EnsureEditorState() {
+  MOZ_ASSERT(IsSingleLineTextControl(false));
+  if (!mInputData.mState) {
+    mInputData.mState = TextControlState::Construct(this);
+  }
+}
+
 TextControlState* HTMLInputElement::GetEditorState() const {
   if (!IsSingleLineTextControl(false)) {
     return nullptr;
   }
 
+  // We've postponed allocating TextControlState, doing that in a const
+  // method is fine.
+  const_cast<HTMLInputElement*>(this)->EnsureEditorState();
+
   MOZ_ASSERT(mInputData.mState,
              "Single line text controls need to have a state"
              " associated with them");
@@ -1085,7 +1097,7 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(HTMLInputElement,
                                                   TextControlElement)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mValidity)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mControllers)
-  if (tmp->IsSingleLineTextControl(false)) {
+  if (tmp->IsSingleLineTextControl(false) && tmp->mInputData.mState) {
     tmp->mInputData.mState->Traverse(cb);
   }
 
@@ -1098,7 +1110,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLInputElement,
                                                 TextControlElement)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mValidity)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mControllers)
-  if (tmp->IsSingleLineTextControl(false)) {
+  if (tmp->IsSingleLineTextControl(false) && tmp->mInputData.mState) {
     tmp->mInputData.mState->Unlink();
   }
 
@@ -1578,7 +1590,12 @@ void HTMLInputElement::GetNonFileValueInternal(nsAString& aValue) const {
   switch (GetValueMode()) {
     case VALUE_MODE_VALUE:
       if (IsSingleLineTextControl(false)) {
-        mInputData.mState->GetValue(aValue, true, /* aForDisplay = */ false);
+        if (mInputData.mState) {
+          mInputData.mState->GetValue(aValue, true, /* aForDisplay = */ false);
+        } else {
+          // Value hasn't been set yet.
+          aValue.Truncate();
+        }
       } else if (!aValue.Assign(mInputData.mValue, fallible)) {
         aValue.Truncate();
       }
@@ -2702,6 +2719,7 @@ nsresult HTMLInputElement::SetValueInternal(
         // of calling this method, you need to maintain SetUserInput() too. FYI:
         // After calling SetValue(), the input type might have been
         //      modified so that mInputData may not store TextControlState.
+        EnsureEditorState();
         if (!mInputData.mState->SetValue(
                 value, aOldValue,
                 forcePreserveUndoHistory
@@ -4455,7 +4473,7 @@ void HTMLInputElement::HandleTypeChange(FormControlType aNewType,
 
   TextControlState::SelectionProperties sp;
 
-  if (GetEditorState()) {
+  if (IsSingleLineTextControl(false) && mInputData.mState) {
     mInputData.mState->SyncUpSelectionPropertiesBeforeDestruction();
     sp = mInputData.mState->GetSelectionProperties();
   }

dom/html/HTMLInputElement.h

@@ -1067,6 +1067,7 @@ class HTMLInputElement final : public TextControlElement,
 
   MOZ_CAN_RUN_SCRIPT void FreeData();
   TextControlState* GetEditorState() const;
+  void EnsureEditorState();
 
   MOZ_CAN_RUN_SCRIPT TextEditor* GetTextEditorFromState();