Resolve an ambiguous function call by casting to StringPiece::size_type

base/string_piece_unittest.cc

 // Copyright (c) 2011 The Chromium 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 <string>
 
 #include "base/string16.h"
 #include "base/string_piece.h"
 #include "base/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 646 matching lines @@
 }
 
 TYPED_TEST(CommonStringPieceTest, CheckConstructors) {
   TypeParam str(TestFixture::as_string("hello world"));
   TypeParam empty;
 
   ASSERT_TRUE(str == BasicStringPiece<TypeParam>(str));
   ASSERT_TRUE(str == BasicStringPiece<TypeParam>(str.c_str()));
   ASSERT_TRUE(TestFixture::as_string("hello") ==
               BasicStringPiece<TypeParam>(str.c_str(), 5));
-  ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(str.c_str(), 0));
+  ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(str.c_str(), 0U));
   ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(NULL));
-  ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(NULL, 0));
+  ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(NULL, 0U));
   ASSERT_TRUE(empty == BasicStringPiece<TypeParam>());
   ASSERT_TRUE(str == BasicStringPiece<TypeParam>(str.begin(), str.end()));
   ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(str.begin(), str.begin()));
   ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(empty));
   ASSERT_TRUE(empty == BasicStringPiece<TypeParam>(empty.begin(), empty.end()));
 }
 
 }  // namespace base