Change default timestamp to 64 bits in all webrtc directories.

webrtc/video/end_to_end_tests.cc

Index: webrtc/video/end_to_end_tests.cc
diff --git a/webrtc/video/end_to_end_tests.cc b/webrtc/video/end_to_end_tests.cc
index 0e02ff8b2e952d9f42509ddeb27eb3e72d652de2..9f7ac59981d461493ad1df2925090b7b9ebe89b8 100644
--- a/webrtc/video/end_to_end_tests.cc
+++ b/webrtc/video/end_to_end_tests.cc
@@ -19,7 +19,6 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/event.h"
-#include "webrtc/base/timeutils.h"
 #include "webrtc/call.h"
 #include "webrtc/call/transport_adapter.h"
 #include "webrtc/common_video/include/frame_callback.h"
@@ -2933,7 +2932,7 @@ void EndToEndTest::TestRtpStatePreservation(bool use_rtx) {
       } else {
         // Verify timestamps are reasonably close.
         uint32_t latest_observed = timestamp_it->second;
-        int32_t timestamp_gap = rtc::TimeDiff(timestamp, latest_observed);
+        int32_t timestamp_gap = timestamp - latest_observed;

[pbos-webrtc, 2016/05/05 15:43:56]

These are uint32_ts and its correctness is probably implementation-defined on
wraparounds.

Though with that said it looks like this was current behavior already since
rtc::TimeDiff was just a - b. Feel free to add a note/TODO.

[honghaiz3, 2016/05/05 17:25:15]

AFAIK, when you subtract two uint32_ts it will correctly return an int value
without wraparound handling. For example 1u - 2u => (int)1. The only catch is to
make sure the resulting variable to be int (int32) type. That is the reason of
recent change of rtc::TimeDiff. Added a short note. 

         EXPECT_LE(std::abs(timestamp_gap), kMaxTimestampGap)
             << "Gap in timestamps (" << latest_observed << " -> "
             << timestamp << ") too large for SSRC: " << ssrc << ".";