Re-enable layer squashing

We've fixed all the know bugs. Hopefully this time it will stick. If you find
that this CL caused a regression, please mark the bug as blocking
http://crbug.com/365701

BUG=365701

Review URL: https://codereview.chromium.org/267343005

git-svn-id: svn://svn.chromium.org/blink/trunk@173696 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

@@ -69,7 +69,7 @@ ImageDataConstructor status=experimental
 IndexedDBExperimental status=experimental
 InputModeAttribute status=experimental
 LangAttributeAwareFormControlUI
-LayerSquashing status=test
+LayerSquashing status=stable
 PrefixedEncryptedMedia status=stable
 LocalStorage status=stable
 Manifest status=test