Revert "remove toString"

This reverts commit 5191880cbf3ee4d122b0d11b4945fbab0784fda7.

Reason for revert: broke flutter

Original change's description:
> remove toString
> 
> toString may have been used by obsolete debugger only
> find out if that is so
> 
> R=​brianosman@google.com,bsalomon@google.com
> 
> Docs-Preview: https://skia.org/?cl=119894
> Bug:830651
> Change-Id: I737f19b7d3fbc869bea2f443fa3b5ed7c1393ffd
> Reviewed-on: https://skia-review.googlesource.com/119894
> Commit-Queue: Cary Clark <caryclark@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,brianosman@google.com,caryclark@google.com,caryclark@skia.org

Change-Id: I9f81de6c3615ee0608bcea9081b77239b4b8816c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 830651
Reviewed-on: https://skia-review.googlesource.com/129340
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>
130 files changed