add ImageGenerator::NewFromData to porting layer

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 8796b0328355f1c5049ee0151454197c74acbc57..97e7475a34ff28dc49b6499d5ecaef86c3c8d7fa 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -7,6 +7,7 @@
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
+#include "SkImageGenerator.h"
 #include "SkImagePriv.h"
 #include "SkImage_Base.h"
 #include "SkReadPixelsRec.h"
@@ -72,6 +73,14 @@ SkData* SkImage::encode(SkImageEncoder::Type type, int quality) const {
     return NULL;
 }
 
+SkImage* SkImage::NewFromData(SkData* data) {
+    if (NULL == data) {
+        return NULL;
+    }
+    SkImageGenerator* generator = SkImageGenerator::NewFromData(data);
+    return generator ? SkImage::NewFromGenerator(generator) : NULL;
+}
+
 SkSurface* SkImage::newSurface(const SkImageInfo& info, const SkSurfaceProps* props) const {
     if (NULL == props) {
         props = &as_IB(this)->props();