RFR: 8267800: Remove the '_dirty' set in BCEscapeAnalyzer

[Denghui Dong]

Hi,

Could I have a review of this change?

The content of `_dirty` in  `BCEscapeAnalyzer` is only updated when processing `_aaload`. And it will not affect the results of the analysis because its content is never used, so I think we should remove this set.

Thanks,
Denghui

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Commit messages:
 - 8267800: Remove the '_dirty' set in BCEscapeAnalyzer

Changes: https://git.openjdk.java.net/jdk/pull/4208/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4208&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267800
  Stats: 9 lines in 2 files changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4208.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4208/head:pull/4208

PR: https://git.openjdk.java.net/jdk/pull/4208