Bug 1310744: Revert "Bug 1300193: Make existing assertion that no longer holds more flexible. r=jandem,nbp", but keep the test.

This now holds, as it should. The test is superseded by the one in this bug, but
it's harmless.

MozReview-Commit-ID: G7HHZLIIr6Y

--HG--
extra : rebase_source : afb8a1fd07ccd200f15bdace325d43e2ce368bbe

js/src/vm/NativeObject-inl.h

@@ -163,7 +163,7 @@ NativeObject::extendDenseElements(ExclusiveContext* cx,
      * long as there is capacity for them.
      */
     if (!nonProxyIsExtensible() || watched()) {
-        MOZ_ASSERT(getDenseCapacity() == 0 || (!watched() && getElementsHeader()->isFrozen()));
+        MOZ_ASSERT(getDenseCapacity() == 0);
         return DenseElementResult::Incomplete;
     }