Revert "Revert "Cache all Charset instances with their aliases""

Fixes the caching bug that non-standard charset name is not correctly
handled.

This reverts commit 8f5d171744cacd52d9831d9dcad79ab70ec00a70.

Bug: 26457745
Bug: 26140874
Change-Id: I73c09bc6ba0e94c8ba499b36b564f0b96976c4e2
2 files changed