8209841: [REDO] Refactor G1ParallelCleaningTask into shared

[Thomas Schatzl]

Hi,

On Wed, 2018-08-22 at 12:20 -0400, Zhengyu Gu wrote:
> This is redo of JDK-8206467.
> 
> - Fixed merging issue in original patch.
> 
> - Based on Thomas comments, moved time tracking of individual
> cleaning task.
> 
> The difference from current G1 implementation:
> 
> - G1StringDedupUnlinkOrOopsDoClosure is passed to
> ParallelCleaningTask as a parameter.
> 
> - Moved initialization of _initial_string_table_size in 
> StringCleaningTask to the initializer list (as Kim suggested)
> 
> - Passes NULL StringDedupUnlinkOrOopsDoClosure to indicate string 
> duduplication is disabled, and removed process_string_dedup parameter
> in StringCleaningTask constructor.
> 
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8209841
> Webrev: http://cr.openjdk.java.net/~zgu/8209841/webrev.00/
> 
> Test:
> 
>    hotspot_gc Linux x64 (fastdebug and release)

looks good. I am putting it through internal testing right now. Will
take a few hours.

Thanks,
  Thomas