Change default timestamp to 64 bits in all webrtc directories.

webrtc/base/logging.h

Index: webrtc/base/logging.h
diff --git a/webrtc/base/logging.h b/webrtc/base/logging.h
index 8c7b3f70e5284a5c0a7b76f69ab5e05ac089a7a8..86945b3883332c6f5058476ad3a5dd1994f58bb3 100644
--- a/webrtc/base/logging.h
+++ b/webrtc/base/logging.h
@@ -147,7 +147,7 @@ class LogMessage {
   // If this is not called externally, the LogMessage ctor also calls it, in
   // which case the logging start time will be the time of the first LogMessage
   // instance is created.
-  static uint32_t LogStartTime();
+  static int64_t LogStartTime();
 
   // Returns the wall clock equivalent of |LogStartTime|, in seconds from the
   // epoch.