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/api/dtmfsender_unittest.cc b/webrtc/api/dtmfsender_unittest.cc
index efe568d..e5fe261 100644
--- a/webrtc/api/dtmfsender_unittest.cc
+++ b/webrtc/api/dtmfsender_unittest.cc
@@ -85,9 +85,9 @@
     // TODO(ronghuawu): Make the timer (basically the rtc::TimeNanos)
     // mockable and use a fake timer in the unit tests.
     if (last_insert_dtmf_call_ > 0) {
-      gap = static_cast<int>(rtc::Time() - last_insert_dtmf_call_);
+      gap = static_cast<int>(rtc::TimeMillis() - last_insert_dtmf_call_);
     }
-    last_insert_dtmf_call_ = rtc::Time();
+    last_insert_dtmf_call_ = rtc::TimeMillis();
 
     LOG(LS_VERBOSE) << "FakeDtmfProvider::InsertDtmf code=" << code
                     << " duration=" << duration