RFR: 8255746: Make PrintCompilation available on a per method level [v2]

[Joshua Cao]

> Example:
> 
> 
> [~/jdk/jdk]$ build/linux-x86_64-server-fastdebug/jdk/bin/java -XX:CompileCommand=PrintCompilation,java.lang.String::length Hello
> CompileCommand: PrintCompilation java/lang/String.length bool PrintCompilation = true
>     223   12       3       java.lang.String::length (11 bytes)
>     405  307       4       java.lang.String::length (11 bytes)
> hello world
> 
> 
> Running `java -XX:+PrintCompilation` still prints every method. This change also moves the declaration of `elapsedTimer`, but it should have insignificant impact on actual elapsed time.
> 
> ---
> 
> Additionally, I make a change to `test/lib-test/jdk/test/whitebox/vm_flags/BooleanTest.java` so that it does not depend on PrintCompilation. The test was failing because it updates global `PrintCompilation` during the middle of the run, but this does not change the value of `PrintCompilationOption` for individual CompileTask directives.
> 
> I modified the test so that it is similar to other [WhiteBox vm_flag test](https://github.com/openjdk/jdk/tree/master/test/lib-test/jdk/test/whitebox/vm_flags). It still tests `VmFlagTest.WHITE_BOX::get/setBooleanVMFlag`, without having to depend on the behavior on the specific flag.

Joshua Cao has updated the pull request incrementally with one additional commit since the last revision:

  Set CompileTask directive on initialization, add tests for
  PrintCompilation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10668/files
  - new: https://git.openjdk.org/jdk/pull/10668/files/552a9a81..2eb4c9c8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10668&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10668&range=00-01

  Stats: 194 lines in 5 files changed: 178 ins; 11 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10668.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10668/head:pull/10668

PR: https://git.openjdk.org/jdk/pull/10668