Add the lazy decoder from PictureFlags to SkImageDecoder

tools/LazyDecodeBitmap.h

Index: tools/LazyDecodeBitmap.h
diff --git a/tools/LazyDecodeBitmap.h b/tools/LazyDecodeBitmap.h
new file mode 100644
index 0000000000000000000000000000000000000000..ecceb94f7edbcc9a742dde6b6096a51be3d54d6e
--- /dev/null
+++ b/tools/LazyDecodeBitmap.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef LazyDecodeBitmap_DEFINED
+#define LazyDecodeBitmap_DEFINED
+
+#include "SkTypes.h"
+
+class SkBitmap;
+
+namespace sk_tools {
+
+/**
+ * Decode the image with DecodeMemoryToTarget but defer the process until it is needed.
+ */
+bool LazyDecodeBitmap(const void* buffer, size_t size, SkBitmap* bitmap);
+
+}
+
+#endif  // LazyDecodeBitmap_DEFINED