ReturnBlobToWrongHeapTest fails because of problems in CodeHeap::contains_blob()

We see failures in test/compiler/codecache/stress/ReturnBlobToWrongHeapTest.java which are cause by problems in CodeHeap::contains_blob() for corner cases with CodeBlobs of zero size:

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (heap.cpp:248), pid=27586, tid=27587
# guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high()) failed: The block to be deallocated 0x00007fffe6666f80 is not within the heap starting with 0x00007fffe6667000 and ending with 0x00007fffe6ba000

The problem is that JDK-8183573 replaced

  virtual bool contains_blob(const CodeBlob* blob) const { return low_boundary() <= (char*) blob && (char*) blob < high(); }

by:

  bool contains_blob(const CodeBlob* blob) const { return contains(blob->code_begin()); }

But that my be wrong in the corner case where the size of the CodeBlob's payload is zero (i.e. the CodeBlob consists only of the 'header' - i.e. the C++ object itself) because in that case CodeBlob::code_begin() points right behind the CodeBlob's header which is a memory location which doesn't belong to the CodeBlob anymore.

This exact corner case is exercised by ReturnBlobToWrongHeapTest which allocates CodeBlobs of size zero (i.e. zero 'payload') with the help of sun.hotspot.WhiteBox.allocateCodeBlob() until the CodeCache fills up. The test first fills the 'non-profiled nmethods' CodeHeap. If the 'non-profiled nmethods' CodeHeap is full, the VM automatically tries to allocate from the 'profiled nmethods' CodeHeap until that fills up as well. But in the CodeCache the 'profiled nmethods' CodeHeap is located right before the non-profiled nmethods' CodeHeap. So if the last CodeBlob allocated from the 'profiled nmethods' CodeHeap has a payload size of zero and uses all the CodeHeaps remaining size, we will end up with a CodeBlob whose code_begin() address will point right behind the actual CodeHeap (i.e. it will point right at the beginning of the adjacent, 'non-profiled nmethods' CodeHeap). This will result in the above guarantee to fire, when we will try to free the last allocated CodeBlob (with sun.hotspot.WhiteBox.freeCodeBlob()).