SkImageEncoder: simplify API

(re-land 248ff02 & 2cb6cb7, with changes)

  - Hide SkImageEncoder class in private header.
  - SkImageEncoder::Type becomes SkEncodedImageFormat
  - SkEncodedFormat becomes SkEncodedImageFormat
  - SkImageEncoder static functions replaced with
    single function EncodeImage()
  - utility wrappers for EncodeImage() are in
    sk_tool_utils.h

TODO: remove link-time registration mechanism.
TODO: clean up clients use of API and flip the flag.
TODO: implement EncodeImage() in chromeium/skia/ext

Change-Id: I47d451e50be4d5c6c130869c7fa7c2857243d9f0
Reviewed-on: https://skia-review.googlesource.com/4909
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-on: https://skia-review.googlesource.com/5186
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Hal Canary <halcanary@google.com>
diff --git a/tests/CodecTest.cpp b/tests/CodecTest.cpp
index dacabca..d15c710 100644
--- a/tests/CodecTest.cpp
+++ b/tests/CodecTest.cpp
@@ -23,6 +23,8 @@
 
 #include "png.h"
 
+#include "sk_tool_utils.h"
+
 #if PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR < 5
     // FIXME (scroggo): Google3 needs to be updated to use a newer version of libpng. In
     // the meantime, we had to break some pieces of SkPngCodec in order to support Google3.
@@ -1102,7 +1104,7 @@
 
     // Encode the image to png.
     sk_sp<SkData> data =
-            sk_sp<SkData>(SkImageEncoder::EncodeData(bm1, SkImageEncoder::kPNG_Type, 100));
+            sk_sp<SkData>(sk_tool_utils::EncodeImageToData(bm1, SkEncodedImageFormat::kPNG, 100));
 
     std::unique_ptr<SkCodec> codec(SkCodec::NewFromData(data));
     REPORTER_ASSERT(r, color_type_match(info.colorType(), codec->getInfo().colorType()));