Add tests for CreateByeDataBlock (#663)

Ensure that all bytes of newly-created Data Block are initialized to
zero.

test/built-ins/ArrayBuffer/init-zero.js

+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-arraybuffer-length
+es6id: 24.1.1.1
+description: All bytes are initialized to zero
+info: |
+    [...]
+    5. Return ? AllocateArrayBuffer(NewTarget, byteLength).
+
+    24.1.1.1 AllocateArrayBuffer
+
+    3. Let block be ? CreateByteDataBlock(byteLength).
+
+    6.2.6.1 CreateByteDataBlock
+
+    1. Assert: size≥0.
+    2. Let db be a new Data Block value consisting of size bytes. If it is
+       impossible to create such a Data Block, throw a RangeError exception.
+    3. Set all of the bytes of db to 0.
+    4. Return db. 
+features: [DataView]
+---*/
+
+var view = new DataView(new ArrayBuffer(9));
+
+assert.sameValue(view.getUint8(0), 0, 'index 0');
+assert.sameValue(view.getUint8(1), 0, 'index 1');
+assert.sameValue(view.getUint8(2), 0, 'index 2');
+assert.sameValue(view.getUint8(3), 0, 'index 3');
+assert.sameValue(view.getUint8(4), 0, 'index 4');
+assert.sameValue(view.getUint8(5), 0, 'index 5');
+assert.sameValue(view.getUint8(6), 0, 'index 6');
+assert.sameValue(view.getUint8(7), 0, 'index 7');
+assert.sameValue(view.getUint8(8), 0, 'index 8');

test/built-ins/TypedArrays/length-arg-init-zeros.js

+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-typedarray-length
+description: All bytes are initialized to zero
+info: >
+  22.2.4.2 TypedArray ( length )
+
+  This description applies only if the TypedArray function is called with at
+  least one argument and the Type of the first argument is not Object.
+
+  ...
+  8. Return ? AllocateTypedArray(constructorName, NewTarget,
+  %TypedArrayPrototype%, elementLength).
+
+  22.2.4.2.1 Runtime Semantics: AllocateTypedArray (constructorName, newTarget,
+  defaultProto [ , length ])
+
+  5. If length was not passed, then
+     ...
+  6. Else,
+     a. Perform ? AllocateTypedArrayBuffer(obj, length).
+
+  22.2.4.2.2 Runtime Semantics: AllocateTypedArrayBuffer
+
+  7. Let data be ? AllocateArrayBuffer(%ArrayBuffer%, byteLength).
+
+  24.1.1.1 AllocateArrayBuffer
+
+  3. Let block be ? CreateByteDataBlock(byteLength).
+
+  6.2.6.1 CreateByteDataBlock
+
+  1. Assert: size≥0.
+  2. Let db be a new Data Block value consisting of size bytes. If it is
+     impossible to create such a Data Block, throw a RangeError exception.
+  3. Set all of the bytes of db to 0.
+  4. Return db. 
+includes: [testTypedArray.js]
+---*/
+
+testWithTypedArrayConstructors(function(TA) {
+  var subject = new TA(9);
+
+  assert.sameValue(subject[0], 0, 'index 0');
+  assert.sameValue(subject[1], 0, 'index 1');
+  assert.sameValue(subject[2], 0, 'index 2');
+  assert.sameValue(subject[3], 0, 'index 3');
+  assert.sameValue(subject[4], 0, 'index 4');
+  assert.sameValue(subject[5], 0, 'index 5');
+  assert.sameValue(subject[6], 0, 'index 6');
+  assert.sameValue(subject[7], 0, 'index 7');
+  assert.sameValue(subject[8], 0, 'index 8');
+});