RFR: 8266435: WBMPImageReader.read() should not truncate the input stream

[Jayathirth D V]

If we use a custom stream and specify limit on stream.read() length, WBMPImageReader.read() doesnt verify whether we are decoded complete data or not. We can check the length of data decoded and rerun the stream.read() or use readFully(). In case of other decoders like BMP we are using readFully(), so i have updated WBMPImageReader.read() to use readFully().

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Commit messages:
 - 8266435: WBMPImageReader.read() should not truncate the input stream

Changes: https://git.openjdk.java.net/jdk/pull/6518/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6518&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266435
  Stats: 122 lines in 2 files changed: 118 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6518.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6518/head:pull/6518

PR: https://git.openjdk.java.net/jdk/pull/6518