Bug 1431041: Fix placeholder-shown when the value of the input is invalid. r=smaug

Wow, the setup for <input type="number"> is really weird :(.

Looking at the callers, this should be sane.

MozReview-Commit-ID: C0ZNNSdg0Hb

dom/html/HTMLInputElement.cpp

@@ -6600,7 +6600,7 @@ HTMLInputElement::IntrinsicState() const
 
   if (PlaceholderApplies() &&
       HasAttr(kNameSpaceID_None, nsGkAtoms::placeholder) &&
-      IsValueEmpty()) {
+      ShouldShowPlaceholder()) {
     state |= NS_EVENT_STATE_PLACEHOLDERSHOWN;
   }
 
@@ -6611,6 +6611,24 @@ HTMLInputElement::IntrinsicState() const
   return state;
 }
 
+bool
+HTMLInputElement::ShouldShowPlaceholder() const
+{
+  MOZ_ASSERT(PlaceholderApplies());
+
+  if (!IsValueEmpty()) {
+    return false;
+  }
+
+  // For number controls, even though the (sanitized) value is empty, there may
+  // be text in the anon text control.
+  if (nsNumberControlFrame* frame = do_QueryFrame(GetPrimaryFrame())) {
+    return frame->AnonTextControlIsEmpty();
+  }
+
+  return true;
+}
+
 void
 HTMLInputElement::AddStates(EventStates aStates)
 {