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/thread.cc b/webrtc/base/thread.cc
index 7cbc972..3971169 100644
--- a/webrtc/base/thread.cc
+++ b/webrtc/base/thread.cc
@@ -482,7 +482,7 @@
 }
 
 bool Thread::ProcessMessages(int cmsLoop) {
-  uint32_t msEnd = (kForever == cmsLoop) ? 0 : TimeAfter(cmsLoop);
+  int64_t msEnd = (kForever == cmsLoop) ? 0 : TimeAfter(cmsLoop);
   int cmsNext = cmsLoop;
 
   while (true) {