RFR: 8263324: Lanai: use the PtrPixelsRow instead of multiplication

[Alexey Ushakov]

Avoid multiplication in address arithmetics

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Commit messages:
 - 8263324: Lanai: use the PtrPixelsRow instead of multiplication

Changes: https://git.openjdk.java.net/lanai/pull/214/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=214&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263324
  Stats: 20 lines in 3 files changed: 7 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/lanai/pull/214.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/214/head:pull/214

PR: https://git.openjdk.java.net/lanai/pull/214