Small nits in Class.java.

Change-Id: I03230089f2bca70d7e843127b08139f99508d700
Fixes IE10 compatibility of stack traces.

Change-Id: I8b909e153bb91b1d6ea84df5712c7aa4786bbcb8
Remove extra frames from JavaScriptException stack.

Currently, JavaScriptException introduces 4 additional stack frames
due to extra wrapping calls in emulation mode. This makes it harder
for users to quickly identify the culprit code especially in tests
if a javascript exception (e.g. TypeError) occurs.

This patch ensures that StackTraceCreator drops these extra frames.
Only remaining extra frame is Exceptions.wrap call. This is slightly
useful as developers can see stack is generated via exception wrapping
so it doesn't worth to deal with the extra complexity required to remove
that frame.

Change-Id: I3b617cf3fc9bd8cc3b94d057a25f996ba91583b3