RFR 8159284: bigapps/Jetty - assert(jfa->last_Java_sp() > sp()) failed with tracing code in use

[Coleen Phillimore]

Summary: Test condition in assert in frame::safe_for_sender() for entry 
frames and return false.

This bug is for a confidential part of the project that needs more 
robustness checks to verify that frame::sender() can be called.

Also refactored into frame::entry_frame_is_safe() because these 
platforms had the same code for entry frames to determine whether it is 
still safe to trust this frame to call sender(). These platforms had 
also the same assert in sender_for_entry_frame() that the sampling code hit.

Tested with our nightly tests on all platforms and bigapps/Jetty.

open webrev at http://cr.openjdk.java.net/~coleenp/8159284.01/webrev

Thanks,
Coleen