Bug 1829189 - Make BeforeSetAttr infallible. r=smaug

rg BeforeSetAttr -l | xargs sed -i 's/nsresult BeforeSetAttr/void BeforeSetAttr/g'
  rg ::BeforeSetAttr -l | xargs sed -i 's/nsresult \(.*\)::BeforeSetAttr/void \1::BeforeSetAttr/g'

Plus trivial fixes, plus clang-format.

The only meaningful changes are in nsXULElement::BeforeSetAttr. Two
things could fail:

chromemargin: I removed it because we don't use the parsed attribute any
other place than here:

  https://searchfox.org/mozilla-central/rev/31f5847a4494b3646edabbdd7ea39cb88509afe2/dom/xul/ChromeObserver.cpp#136

And that deals just fine with it not being parsed.

usercontextid: We have a debug assertion that we don't dynamically change it.
I kept it but I don't think it's worth failing to set the attribute on release for that

Differential Revision: https://phabricator.services.mozilla.com/D176069

dom/html/HTMLTextAreaElement.cpp

@@ -822,9 +822,9 @@ void HTMLTextAreaElement::UnbindFromTree(bool aNullParent) {
   UpdateState(false);
 }
 
-nsresult HTMLTextAreaElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
-                                            const nsAttrValueOrString* aValue,
-                                            bool aNotify) {
+void HTMLTextAreaElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                        const nsAttrValueOrString* aValue,
+                                        bool aNotify) {
   if (aNotify && aName == nsGkAtoms::disabled &&
       aNameSpaceID == kNameSpaceID_None) {
     mDisabledChanged = true;