Add Vibration API layout tests that inspect internal state.

Source/modules/vibration/testing/InternalsVibration.h

Index: Source/modules/vibration/testing/InternalsVibration.h
diff --git a/Source/modules/vibration/testing/InternalsVibration.h b/Source/modules/vibration/testing/InternalsVibration.h
index 7dbe566120bc6bf96a56c45201de78357338a072..4f0cf3e84caf345464d48913c9be982f9c21cc56 100644
--- a/Source/modules/vibration/testing/InternalsVibration.h
+++ b/Source/modules/vibration/testing/InternalsVibration.h
@@ -31,6 +31,8 @@
 #ifndef InternalsVibration_h
 #define InternalsVibration_h
 
+#include "wtf/Vector.h"
+
 namespace WebCore {
 
 class Document;
@@ -39,6 +41,7 @@ class Internals;
 class InternalsVibration {
 public:
     static bool isVibrating(Internals*, Document*);
+    static Vector<unsigned> pendingVibrationPattern(Internals*, Document*);
 };
 
 } // namespace WebCore