RFR: 8155259: Suspicious buffer allocation in com.sun.tools.javac.file.BaseFileManager

[Archie L. Cobbs]

JDK-8155259 notes that in `BaseFileManager` this code:

ByteBuffer.allocate(capacity + capacity>>1)

is actually equivalent (assuming no overflow) to:

ByteBuffer.allocate(capacity)

because in Java the `+` operator has higher precedence than the `>>` operator.

In the bug it is suggested that this be changed to reflect the presumed original intent to over-allocate by 50%, i.e.:

ByteBuffer.allocate(capacity + (capacity>>1))

however, this patch is more conservative in that it leaves the existing behavior alone and instead just simplifies it to:

ByteBuffer.allocate(capacity)

allowing us to at least resolve JDK-8155259.

-------------

Commit messages:
 - 8155259: Suspicious buffer allocation in com.sun.tools.javac.file.BaseFileManager

Changes: https://git.openjdk.org/jdk/pull/10803/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10803&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8155259
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10803.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10803/head:pull/10803

PR: https://git.openjdk.org/jdk/pull/10803