RFR: JDK-8263559: Add missing initializers to VM_PopulateDumpSharedSpace [v2]

[Thomas Stuefe]

> Trivial.
> 
> Sonarcloud reports missing initializers in VM_PopulateDumpSharedSpace. I don't see how this could lead to an error, since these members are initialized later, but for cleanliness sake lets initialize them.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  Remove explicit NULL resets

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2996/files
  - new: https://git.openjdk.java.net/jdk/pull/2996/files/d7bd9e6f..fe44ca64

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2996&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2996&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2996.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2996/head:pull/2996

PR: https://git.openjdk.java.net/jdk/pull/2996