Update to use nativehelper/JNIPlatformHelp.h

Reflects refactoring of JNI helper code that depends on private
methods within libnativehelper.

Bug: 151443957
Test: m
Change-Id: I7696163cb0e87fd9419ec384553969e71c68f1f3
Merged-In: I7696163cb0e87fd9419ec384553969e71c68f1f3
Exempt-From-Owner-Approval: cherry pick
Tag: #refactor
(cherry picked from commit c7894a088b1561aaf0a49a81cd73d71b3f4ac748)