RFR: 8276990: Memory leak in invoker.c fillInvokeRequest() during JDI operations [v3]

[Roman Kennke]

> We observe a native memory leak when repeating JDI operations from Eclipse in a debuggee JVM. See bug report for details.
> 
> AFAICT, this happens because we override methodSignature of a possible pre-existing request object. I am not sure if there is a better place to deallocate the signature.
> 
> Also, I am not sure how to make an automated test for this. We (that is, the customer that reported the problem) verified that the memory leak disappears with the fix.
> 
> Testing:
>  - [x] tier1
>  - [ ] tier2
>  - [ ] tier3
>  - [ ] Customer confirming fix of memory leak

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Deallocate methodSignature in deleteGlobalArgumentRefs()

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7306/files
  - new: https://git.openjdk.java.net/jdk/pull/7306/files/4b62941b..a273574b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7306&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7306&range=01-02

  Stats: 9 lines in 1 file changed: 4 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7306.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7306/head:pull/7306

PR: https://git.openjdk.java.net/jdk/pull/7306