Revert of change pixel-serializer to support reencoding existing data (patchset #5 id:80001 of https://codereview.chromium.org/1373683003/ )

Reason for revert:
Need to somehow get access to encoders in chrome -- link error on the roll since SkImageEncoder is not built as part of chrome.

Original issue's description:
> change pixel-serializer to support reencoding existing data
>
> Trying to evolve this interface so it can
> - support rich set of backend-encoders (including ones like ETC1 that can cheaply convert to KXT
> - allow for encoding images as well as bitmaps (e.g. for picture serialization)
> - perhaps replace SkImageEncoder as an API (assuming we create a factory that returns a serializer given a format)
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/13f48dc85aa68a60da66aaf39c93d527d11d1278

TBR=scroggo@google.com,msarett@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1371983003
diff --git a/tests/ImageTest.cpp b/tests/ImageTest.cpp
index e022077..0b27af9 100644
--- a/tests/ImageTest.cpp
+++ b/tests/ImageTest.cpp
@@ -119,8 +119,8 @@
     bool didEncode() const { return fDidEncode; }
 
 protected:
-    SkData* onReencodeData(SkData*) override {
-        return nullptr;
+    bool onUseEncodedData(const void*, size_t) override {
+        return false;
     }
 
     SkData* onEncodePixels(const SkImageInfo&, const void*, size_t) override {