Remove SkImageRef and related functionality.

src/ports/SkImageDecoder_empty.cpp

Index: src/ports/SkImageDecoder_empty.cpp
diff --git a/src/ports/SkImageDecoder_empty.cpp b/src/ports/SkImageDecoder_empty.cpp
index ae0fc36325485ba0f94e6de3a9e8313a246b7f15..a3503e42bd81b0cc691f7480cf69c2b169a42aba 100644
--- a/src/ports/SkImageDecoder_empty.cpp
+++ b/src/ports/SkImageDecoder_empty.cpp
@@ -147,9 +147,3 @@ bool SkImageEncoder::encodeFile(const char file[], const SkBitmap& bm, int quali
     return false;
 }
 /////////////////////////////////////////////////////////////////////////
-
-// Empty implementation for SkImages.
-
-#include "SkImages.h"
-
-void SkImages::InitializeFlattenables() {}