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/tools/picture_utils.cpp b/tools/picture_utils.cpp
index 43ca2f0..84925b4 100644
--- a/tools/picture_utils.cpp
+++ b/tools/picture_utils.cpp
@@ -17,6 +17,8 @@
 #include "SkStream.h"
 #include "SkString.h"
 
+#include "sk_tool_utils.h"
+
 namespace sk_tools {
     void force_all_opaque(const SkBitmap& bitmap) {
         SkASSERT(kN32_SkColorType == bitmap.colorType());
@@ -63,7 +65,7 @@
             partialPath.set(dirPath);
         }
         SkString fullPath = SkOSPath::Join(partialPath.c_str(), baseName.c_str());
-        if (SkImageEncoder::EncodeFile(fullPath.c_str(), bm, SkImageEncoder::kPNG_Type, 100)) {
+        if (sk_tool_utils::EncodeImageToFile(fullPath.c_str(), bm, SkEncodedImageFormat::kPNG, 100)) {
             return true;
         } else {
             SkDebugf("Failed to write the bitmap to %s.\n", fullPath.c_str());