Make $H a protected name

Change-Id: I7b87987f2a1f66806da0bf5a8237ba373d632e3a
Revert "Make Impl.getHashCode Closure Compilation Compatible"

This reverts commit 8a219f14532ea87a19a1840dea564d1a0adf30e5.

Change-Id: If105298a7a7a9cc54f75e269a9dfcc16bc3fe6eb