Remove SK_ENABLE_LIBPNG define as it is no longer needed by Android.

src/images/SkImageEncoder_Factory.cpp

 
 /*
  * Copyright 2009 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkImageEncoder.h"
 #include "SkTRegistry.h"
 
 typedef SkTRegistry<SkImageEncoder*, SkImageEncoder::Type> EncodeReg;
 
 // Can't use the typedef here because of complex C++ corner cases
 template EncodeReg* SkTRegistry<SkImageEncoder*, SkImageEncoder::Type>::gHead;
 
-#ifdef SK_ENABLE_LIBPNG
-    extern SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type);
-#endif
-
 SkImageEncoder* SkImageEncoder::Create(Type t) {
     SkImageEncoder* codec = NULL;
     const EncodeReg* curr = EncodeReg::Head();
     while (curr) {
         if ((codec = curr->factory()(t)) != NULL) {
             return codec;
         }
         curr = curr->next();
     }
-#ifdef SK_ENABLE_LIBPNG
-    if ((codec = sk_libpng_efactory(t)) != NULL) {
-        return codec;
-    }
-#endif
     return NULL;
 }