RFR: 8262910: Cleanup THREAD/TRAPS/naming and typing issues in ObjectMonitor and related code [v2]

[David Holmes]

> ObjectMonitors can only be used by JavaThreads (modulo some interactions with hashcodes and deflation) but we use "Thread*" almost everywhere mainly due to use of TRAPS (and TRAPS will itself use JavaThread once JDK-8252685 is done). Also some uses of TRAPS in the API's are wrong as, for example, monitor entry can never throw an exception.
> 
> So this cleanup tackles:
> - remove incorrect use of TRAPS
> - change "Thread*" to "JavaThread*" where applicable
> - don't use THREAD for things not related to exception processing
> - standardise the naming so that we have "JavaThread* current" rather a mix if Self/THREAD/jt etc.
> - remove unnecessary as_Java_thread() conversions
> - other misc cleanup I noticed in some functions
> 
> The cleanup is predominantly in objectMonitor.* and synchronizer.* but with a fan out to the users of those APIs. No attempt is made to cleanup the callers beyond ensuring we have a suitable JavaThread reference for the calls. 
> 
> Thanks,
> David

David Holmes has updated the pull request incrementally with two additional commits since the last revision:

 - ObjectMonitor::exit can't actually throw IMSE so replaced TRAPS with JavaThread* current
 - Style fix: Thread *  -> Thread* in type declarations

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2802/files
  - new: https://git.openjdk.java.net/jdk/pull/2802/files/6e334d08..c764b038

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2802&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2802&range=00-01

  Stats: 18 lines in 5 files changed: 0 ins; 2 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2802.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2802/head:pull/2802

PR: https://git.openjdk.java.net/jdk/pull/2802