RFR(XS): 8055946: assert(result == NULL || result->is_oop()) failed: must be oop

[Roland Westrelin]

When a frame is popped by JVMTI, we deoptimize the top 2 frames: the top one to pop it, the caller frame so that we can re-execute the invoke. When the caller frame is deoptimized, even if the top frame is expected to return a value, there’s no return value available because execution of the top frame did not complete.

http://cr.openjdk.java.net/~roland/8055946/webrev.00/

Roland.