RFR: 8252981: ObjectMonitor::object() cleanup changes extracted from JDK-8247281

[Daniel D.Daugherty]

This is a trivial review request. This changeset was tested with Mach5 Tier[1-3],4,5,6,7,8
testing along with JDK-8252980 and JDK-8247281.

Since Erik and I are both contributors, we will need one other reviewer.

This sub-task is tracking ObjectMonitor::object() cleanup changes
extracted from Erik's work on JDK-8247281. This extraction is done
to ease the code review for the JDK-8247281 changes.

Here's the core cleanup:

diff -r fd7f6a424cd1 src/hotspot/share/runtime/objectMonitor.hpp
--- a/src/hotspot/share/runtime/objectMonitor.hpp Fri Aug 28 16:43:09 2020 -0400
+++ b/src/hotspot/share/runtime/objectMonitor.hpp Wed Sep 02 17:22:56 2020 -0400
@@ -328,9 +328,9 @@

  public:

- void* object() const;
- void* object_addr();
- void set_object(void* obj);
+ oop object() const;
+ oop* object_addr();
+ void set_object(oop obj);
   void release_set_allocation_state(AllocationState s);
   void set_allocation_state(AllocationState s);
   AllocationState allocation_state() const;

and those type changes ripple into the other files.

Note: The type for the ObjectMonitor::_object field is intentionally not
being changed from "void*" in this changeset. That will be done in JDK-8247281.

-------------

Commit messages:
 - 8252981: ObjectMonitor::object() cleanup changes extracted from JDK-8247281

Changes: https://git.openjdk.java.net/jdk/pull/114/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=114&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252981
  Stats: 45 lines in 8 files changed: 1 ins; 0 del; 44 mod
  Patch: https://git.openjdk.java.net/jdk/pull/114.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/114/head:pull/114

PR: https://git.openjdk.java.net/jdk/pull/114