Revert "SkStream: remove some WStream functions from public api"

This reverts commit 8b681105077393ce8fb5bef0c1b55461ac2a5792.

Reason for revert: breaks bots

Original change's description:
> SkStream: remove some WStream functions from public api
> 
> move functions to SkStringPriv.h
> 
> also add SkStrAppendU32Hex() function, and re-write
> SkString::insertHex() to use SkStrAppendU32Hex.
> 
> add unit tests.
> 
> Change-Id: Ieda98fb4106db71565b607e593713a91a5ddd892
> Reviewed-on: https://skia-review.googlesource.com/151986
> Reviewed-by: Cary Clark <caryclark@google.com>
> Commit-Queue: Hal Canary <halcanary@google.com>

TBR=halcanary@google.com,bungeman@google.com,caryclark@google.com,reed@google.com

Change-Id: Idbac615092f46c18b38e08385dafba20930f0ff0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/152121
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
15 files changed