[jdk8u-dev] RFR: 8348228: Major performance regression in GetMethodDeclaringClass and other JVMTI Method functions

[Zhengyu Gu]

Please review this patch for the parity of Oracle's [JDK-8185348](https://bugs.openjdk.org/browse/JDK-8185348).

Oracle's patch is non-public. This patch is based on @sspitsyn's comments in JDK-8185348 and consistent with JDK9's implementation.

Before patch, slowjvmti test case from JDK-8185348:
16366ms

After patch:
3ms

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

Commit messages:
 - 8348228: Major performance regression in GetMethodDeclaringClass and other JVMTI Method functions

Changes: https://git.openjdk.org/jdk8u-dev/pull/656/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=656&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348228
  Stats: 8 lines in 2 files changed: 5 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/656.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/656/head:pull/656

PR: https://git.openjdk.org/jdk8u-dev/pull/656