Changed blob to use DataSlice with Arc in order to limit wasteful copying of byte vector

tests/unit/script/dom/blob.rs

@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use script::dom::blob::{DataSlice};
+use std::sync::Arc;
+
+#[test]
+fn test_data_slice_without_start_end_should_match_buffer_size() {
+    let bytes = Arc::new(vec![1u8, 2u8, 3u8]);
+    let data = DataSlice::new(bytes, None, None);
+    assert_eq!(data.size(), 3);
+}
+
+#[test]
+fn test_data_slice_should_prevent_reverse_bounds() {
+    let bytes = Arc::new(vec![1u8, 2, 3, 4, 5]);
+    let start = Some(3);
+    let end = Some(1);
+
+    let data = DataSlice::new(bytes, start, end);
+    assert_eq!(data.size(), 0);
+}
+
+#[test]
+fn test_data_slice_should_respect_correct_bounds() {
+    let bytes = Arc::new(vec![1u8, 2, 3, 4, 5]);
+    let start = Some(1);
+    let end = Some(3);
+
+    let data = DataSlice::new(bytes, start, end);
+    let expected = [2u8, 3];
+    assert_eq!(&expected, data.get_bytes());
+}