Integrated: 8255149: Lanai: DrawImage/IncorrectAlphaConversionBicubic.java failure

[Alexey Ushakov]

Handled premultiplied source textures

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Commit messages:
 - 8255149: Lanai: DrawImage/IncorrectAlphaConversionBicubic.java failure

Changes: https://git.openjdk.java.net/lanai/pull/121/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=121&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255149
  Stats: 8 lines in 3 files changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/lanai/pull/121.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/121/head:pull/121

PR: https://git.openjdk.java.net/lanai/pull/121