Change default timestamp to 64 bits in all webrtc directories.

BUG=
R=pbos@webrtc.org, pthatcher@webrtc.org, solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/1835053002 .

Cr-Commit-Position: refs/heads/master@{#12646}
diff --git a/webrtc/base/nullsocketserver_unittest.cc b/webrtc/base/nullsocketserver_unittest.cc
index 4f22c38..e18afb2 100644
--- a/webrtc/base/nullsocketserver_unittest.cc
+++ b/webrtc/base/nullsocketserver_unittest.cc
@@ -37,7 +37,7 @@
 }
 
 TEST_F(NullSocketServerTest, TestWait) {
-  uint32_t start = Time();
+  int64_t start = TimeMillis();
   ss_.Wait(200, true);
   // The actual wait time is dependent on the resolution of the timer used by
   // the Event class. Allow for the event to signal ~20ms early.