will write a custom one for blink later

BUG=skia:
TBR=
NOTRY=True

Review URL: https://codereview.chromium.org/810603003

include/core/SkImageGenerator.h

@@ -116,6 +116,13 @@ public:
     bool getYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                        SkYUVColorSpace* colorSpace);
 
+    /**
+     *  If the default image decoder system can interpret the specified (encoded) data, then
+     *  this returns a new ImageGenerator for it. Otherwise this returns NULL. Either way
+     *  the caller is still responsible for managing their ownership of the data.
+     */
+    static SkImageGenerator* NewFromData(SkData*);
+
 protected:
     virtual SkData* onRefEncodedData();
     virtual bool onGetInfo(SkImageInfo* info);

src/ports/SkImageGenerator_none.cpp

@@ -0,0 +1,12 @@
+/*
+ * Copyright 2015 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 "SkImageGenerator.h"
+
+SkImageGenerator* SkImageGenerator::NewFromData(SkData*) {
+    return NULL;
+}