Simplify UTF16LE_Encode and add unittest.

core/src/fxcrt/fx_basic_wstring_unittest.cpp

+// Copyright 2014 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "../../../testing/fx_string_testhelpers.h"
+#include "../../include/fxcrt/fx_basic.h"
+
+#define ByteStringLiteral(str) CFX_ByteString(FX_BSTRC(str))
+
+TEST(fxcrt, WideStringUTF16LE_Encode) {
+  struct UTF16LEEncodeCase {
+    CFX_WideString ws;
+    CFX_ByteString bs;
+  } utf16le_encode_cases[] = {
+    { L"", ByteStringLiteral("\0\0") },
+    { L"abc", ByteStringLiteral("a\0b\0c\0\0\0") },
+    { L"abcdef", ByteStringLiteral("a\0b\0c\0d\0e\0f\0\0\0") },
+    { L"abc\0def", ByteStringLiteral("a\0b\0c\0\0\0") },
+    { L"\xaabb\xccdd", ByteStringLiteral("\xbb\xaa\xdd\xcc\0\0") },
+    { L"\x3132\x6162", ByteStringLiteral("\x32\x31\x62\x61\0\0") },
+  };
+
+  for (size_t i = 0; i < FX_ArraySize(utf16le_encode_cases); ++i) {
+    EXPECT_EQ(utf16le_encode_cases[i].bs,
+        utf16le_encode_cases[i].ws.UTF16LE_Encode())
+        << " for case number " << i;
+  }
+}