Bug 1340483 - Part 3. Enable preview function only when input is marked as autofill field. r=heycam

MozReview-Commit-ID: FFqYJ3icRd7

dom/html/HTMLTextAreaElement.cpp

@@ -62,6 +62,7 @@ HTMLTextAreaElement::HTMLTextAreaElement(already_AddRefed<mozilla::dom::NodeInfo
     mDisabledChanged(false),
     mCanShowInvalidUI(true),
     mCanShowValidUI(true),
+    mIsPreviewEnabled(false),
     mState(this)
 {
   AddMutationObserver(this);
@@ -345,6 +346,24 @@ HTMLTextAreaElement::GetPreviewValue(nsAString& aValue)
   mState.GetPreviewText(aValue);
 }
 
+NS_IMETHODIMP_(void)
+HTMLTextAreaElement::EnablePreview()
+{
+  if (mIsPreviewEnabled) {
+    return;
+  }
+
+  mIsPreviewEnabled = true;
+  // Reconstruct the frame to append an anonymous preview node
+  nsLayoutUtils::PostRestyleEvent(this, nsRestyleHint(0), nsChangeHint_ReconstructFrame);
+}
+
+NS_IMETHODIMP_(bool)
+HTMLTextAreaElement::IsPreviewEnabled()
+{
+  return mIsPreviewEnabled;
+}
+
 nsresult
 HTMLTextAreaElement::SetValueInternal(const nsAString& aValue,
                                       uint32_t aFlags)