RFR: JDK-8289799: Build warning in methodData.cpp memset zero-length parameter

[Thomas Stuefe]

Trivial fix for a compiler warning we see in our CI on Fedora 12 with GCC 8.3:


void Copy::pd_zero_to_bytes(void*, size_t)' at /home/ubuntu/client_home/workspace/build-user-branch-linux_x86_64/SapMachine/src/hotspot/cpu/x86/copy_x86.hpp:59:15,
    inlined from 'static void Copy::zero_to_bytes(void*, size_t)' at /home/ubuntu/client_home/workspace/build-user-branch-linux_x86_64/SapMachine/src/hotspot/share/utilities/copy.hpp:298:21,
    inlined from 'void MethodData::initialize()' at

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Commit messages:
 - Test for size > 0 before zeroing

Changes: https://git.openjdk.org/jdk/pull/9390/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9390&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289799
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9390.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9390/head:pull/9390

PR: https://git.openjdk.org/jdk/pull/9390