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

net/quic/platform/impl/quic_chromium_clock_test.cc

Index: net/quic/platform/impl/quic_chromium_clock_test.cc
diff --git a/net/quic/core/quic_clock_test.cc b/net/quic/platform/impl/quic_chromium_clock_test.cc
similarity index 81%
rename from net/quic/core/quic_clock_test.cc
rename to net/quic/platform/impl/quic_chromium_clock_test.cc
index 2f7b6402792d72d312584022e37f76ef066b46c4..562a15655177705069a4006f4cc7e230f8668839 100644
--- a/net/quic/core/quic_clock_test.cc
+++ b/net/quic/platform/impl/quic_chromium_clock_test.cc
@@ -2,15 +2,15 @@
 // 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 "net/quic/platform/impl/quic_chromium_clock.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace net {
 namespace test {
 
-TEST(QuicClockTest, Now) {
-  QuicClock clock;
+TEST(QuicChromiumClockTest, Now) {
+  QuicChromiumClock clock;
 
   QuicTime start(base::TimeTicks::Now());
   QuicTime now = clock.ApproximateNow();
@@ -20,8 +20,8 @@ TEST(QuicClockTest, Now) {
   EXPECT_LE(now, end);
 }
 
-TEST(QuicClockTest, WallNow) {
-  QuicClock clock;
+TEST(QuicChromiumClockTest, WallNow) {
+  QuicChromiumClock clock;
 
   base::Time start = base::Time::Now();
   QuicWallTime now = clock.WallNow();