add runtime option to provide data->imagegenerator factory

tools/LazyDecodeBitmap.cpp

Index: tools/LazyDecodeBitmap.cpp
diff --git a/tools/LazyDecodeBitmap.cpp b/tools/LazyDecodeBitmap.cpp
index 6c655da9e97624775c12a8d807c06882439edd1b..bcd8cad44da3568820411513fd7662c47da94810 100644
--- a/tools/LazyDecodeBitmap.cpp
+++ b/tools/LazyDecodeBitmap.cpp
@@ -28,7 +28,7 @@ bool sk_tools::LazyDecodeBitmap(const void* src, size_t length, SkBitmap* dst) {
         return false;
     }
 
-    SkAutoTDelete<SkImageGenerator> gen(SkImageGenerator::NewFromData(data));
+    SkAutoTDelete<SkImageGenerator> gen(SkImageGenerator::NewFromEncoded(data));
     if (NULL == gen.get()) {
         return false;
     }