Import FileAPI tests from web-platform-tests

LayoutTests/imported/web-platform-tests/FileAPI/support/Blob.js

+function test_blob(fn, expectations) {
+  var expected = expectations.expected,
+      type = expectations.type,
+      desc = expectations.desc;
+
+  var t = async_test(desc);
+  t.step(function() {
+    var blob = fn();
+    assert_true(blob instanceof Blob);
+    assert_false(blob instanceof File);
+    assert_equals(blob.type, type);
+    assert_equals(blob.size, expected.length);
+
+    var fr = new FileReader();
+    fr.onload = t.step_func_done(function(event) {
+      assert_equals(this.result, expected);
+    }, fr);
+    fr.onerror = t.step_func(function(e) {
+      assert_unreached("got error event on FileReader");
+    });
+    fr.readAsText(blob, "UTF-8");
+  });
+}
+
+function test_blob_binary(fn, expectations) {
+  var expected = expectations.expected,
+      type = expectations.type,
+      desc = expectations.desc;
+
+  var t = async_test(desc);
+  t.step(function() {
+    var blob = fn();
+    assert_true(blob instanceof Blob);
+    assert_false(blob instanceof File);
+    assert_equals(blob.type, type);
+    assert_equals(blob.size, expected.length);
+
+    var fr = new FileReader();
+    fr.onload = t.step_func_done(function(event) {
+      assert_true(this.result instanceof ArrayBuffer,
+                  "Result should be an ArrayBuffer");
+      assert_array_equals(new Uint8Array(this.result), expected);
+    }, fr);
+    fr.onerror = t.step_func(function(e) {
+      assert_unreached("got error event on FileReader");
+    });
+    fr.readAsArrayBuffer(blob);
+  });
+}