Move TypedArrayUtils to common

It belongs here since the renderers will use it

src/common/TypedArrayUtils.ts

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+/**
+ * polyfill for TypedArray.fill
+ * This is needed to support .fill in all safari versions and IE 11.
+ */
+
+type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
+  | Int8Array | Int16Array | Int32Array
+  | Float32Array | Float64Array;
+
+export function fill<T extends TypedArray>(array: T, value: number, start?: number, end?: number): T {
+  // all modern engines that support .fill
+  if (array.fill) {
+    return array.fill(value, start, end) as T;
+  }
+  return fillFallback(array, value, start, end);
+}
+
+export function fillFallback<T extends TypedArray>(array: T, value: number, start: number = 0, end: number = array.length): T {
+  // safari and IE 11
+  // since IE 11 does not support Array.prototype.fill either
+  // we cannot use the suggested polyfill from MDN
+  // instead we simply fall back to looping
+  if (start >= array.length) {
+    return array;
+  }
+  start = (array.length + start) % array.length;
+  if (end >= array.length) {
+    end = array.length;
+  } else {
+    end = (array.length + end) % array.length;
+  }
+  for (let i = start; i < end; ++i) {
+    array[i] = value;
+  }
+  return array;
+}