Temporarily disable firefox tests, too unreliable
Temporarily disable firefox tests, too unreliable

PolymerLabs/code-sample-editor,PolymerLabs/code-sample-editor-package,google/playground-elements,google/playground-elements,PolymerLabs/code-sample-editor,PolymerLabs/playground-elements,PolymerLabs/playground-elements,google/playground-elements,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor,PolymerLabs/playground-elements