add SkImage::newSurface

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index f11900dcaa29e7fa748d70f5c641280081bb383d..cbde961b7838ed5902c6796ffe963d903d63c49b 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -9,14 +9,7 @@
 #include "SkCanvas.h"
 #include "SkImagePriv.h"
 #include "SkImage_Base.h"
-
-static SkImage_Base* as_IB(SkImage* image) {
-    return static_cast<SkImage_Base*>(image);
-}
-
-static const SkImage_Base* as_IB(const SkImage* image) {
-    return static_cast<const SkImage_Base*>(image);
-}
+#include "SkSurface.h"
 
 uint32_t SkImage::NextUniqueID() {
     static int32_t gUniqueID;
@@ -91,6 +84,13 @@ SkData* SkImage::encode(SkImageEncoder::Type type, int quality) const {
     return NULL;
 }
 
+SkSurface* SkImage::newSurface(const SkImageInfo& info, const SkSurfaceProps* props) const {
+    if (NULL == props) {
+        props = &as_IB(this)->props();
+    }
+    return as_IB(this)->onNewSurface(info, *props);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 static bool raster_canvas_supports(const SkImageInfo& info) {