A trivial fix. [JDK-8285447](https://bugs.openjdk.org/browse/JDK-8285447) intends to change the initial batch size only for a stack walker with an estimated stack depth. For stack walkers without user-supplied estimated stack depth, the initial batch size is changed to 3 which is a bug. This causes the stack walker to fetch the second batch after walking 2 frames.
------------- Commit messages: - 8316305: Initial buffer size of StackWalker is too small caused by JDK-8285447 Changes: https://git.openjdk.org/jdk/pull/15749/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15749&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8316305 Stats: 8 lines in 1 file changed: 0 ins; 1 del; 7 mod Patch: https://git.openjdk.org/jdk/pull/15749.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15749/head:pull/15749 PR: https://git.openjdk.org/jdk/pull/15749
