add ImageGenerator::NewFromData to porting layer

src/ports/SkImageGenerator_none.cpp

Index: src/ports/SkImageGenerator_none.cpp
diff --git a/src/ports/SkImageGenerator_none.cpp b/src/ports/SkImageGenerator_none.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..78d408aa355027ef58408da1108640b4ef75de45
--- /dev/null
+++ b/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;
+}