Ensure proper this value in tail deleted frames.


== Running test suite: Debugger.TailDeletedFrames.ThisValue
-- Running test case: Debugger.TailDeletedFrames.Scopes
PAUSED
CALL STACK:
0: [F] a
  this: aThis - 2
1: -F- b
  this: bThis - 1
2: -F- c
  this: cThis - 0
3: [F] startABC
  this: undefined
4: [P] Global Code
  this: c - 
RESUMED