Bug 1429125: Enable lazy frame construction in the browser chrome, but not XUL yet. r=heycam,tnikkel

This is on top of the patch to re-enable them in shadow trees for bug 1429088.

MozReview-Commit-ID: 3dwQ9J5nFcS

layout/base/nsCSSFrameConstructor.cpp

@@ -7222,8 +7222,8 @@ nsCSSFrameConstructor::MaybeConstructLazily(Operation aOperation,
                                             nsIContent* aContainer,
                                             nsIContent* aChild)
 {
-  if (mPresShell->GetPresContext()->IsChrome() || !aContainer ||
-      aContainer->IsInNativeAnonymousSubtree() || aContainer->IsXULElement()) {
+  if (!aContainer || aContainer->IsInNativeAnonymousSubtree() ||
+      aContainer->IsXULElement()) {
     return false;
   }