RFR: 8255216: ciEnv::_break_at_compile isn't in use [v3]

[Dan]

> _break_at_compile is no longer in use and can be safely removed.
> No new code, and Tier1 tests succeed after code is removed.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8255216

Dan has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8255216: ciEnv::_break_at_compile isn't in use
  
  _break_at_compile is no longer in use and can be safely removed.
  No new code, and Tier1 tests succeed after code is removed.
  
  Bug: https://bugs.openjdk.java.net/browse/JDK-8255216

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1806/files
  - new: https://git.openjdk.java.net/jdk/pull/1806/files/bbbda14e..efbd3e45

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1806&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1806&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1806.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1806/head:pull/1806

PR: https://git.openjdk.java.net/jdk/pull/1806