Add a QuicChromiumClock and make QuicClock abstract to match internal code.

net/quic/core/quic_clock_test.cc

-// Copyright (c) 2012 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 "net/quic/platform/api/quic_clock.h"
-
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace net {
-namespace test {
-
-TEST(QuicClockTest, Now) {
-  QuicClock clock;
-
-  QuicTime start(base::TimeTicks::Now());
-  QuicTime now = clock.ApproximateNow();
-  QuicTime end(base::TimeTicks::Now());
-
-  EXPECT_LE(start, now);
-  EXPECT_LE(now, end);
-}
-
-TEST(QuicClockTest, WallNow) {
-  QuicClock clock;
-
-  base::Time start = base::Time::Now();
-  QuicWallTime now = clock.WallNow();
-  base::Time end = base::Time::Now();
-
-  // If end > start, then we can check now is between start and end.
-  if (end > start) {
-    EXPECT_LE(static_cast<uint64_t>(start.ToTimeT()), now.ToUNIXSeconds());
-    EXPECT_LE(now.ToUNIXSeconds(), static_cast<uint64_t>(end.ToTimeT()));
-  }
-}
-
-}  // namespace test
-}  // namespace net