Revert "SkImageEncoder::* going away"

Breaks 5 compiles on google3.

This reverts commit 3489b2b727bfb725d45208049e82309280b79ad8.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> SkImageEncoder::* going away
> 
> Approval from https://review.skia.org/5006
> TBR=reed@google.com
> 
> Change-Id: Ib5fb1b624594598e2316f9247069ecd207d7a974
> Reviewed-on: https://skia-review.googlesource.com/5751
> Reviewed-by: Hal Canary <halcanary@google.com>
> Commit-Queue: Hal Canary <halcanary@google.com>
> 

TBR=halcanary@google.com,reed@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I0c0b863056c90435374769e85fb08c1b2f5113a2
Reviewed-on: https://skia-review.googlesource.com/5760
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Herb Derby <herb@google.com>
diff --git a/public.bzl b/public.bzl
index 8bebd19..e17352b 100644
--- a/public.bzl
+++ b/public.bzl
@@ -590,6 +590,7 @@
     # Turn on a few Google3-specific build fixes.
     "GOOGLE3",
     # Staging flags for API changes
+    "SK_SUPPORT_LEGACY_IMAGE_ENCODER_CLASS",
     # Temporarily Disable analytic AA for Google3
     "SK_NO_ANALYTIC_AA",
 ]