Change rtc::TimeNanos and rtc::TimeMicros return value from uint64_t to int64_t.

webrtc/modules/video_coding/codecs/test/videoprocessor.cc

Index: webrtc/modules/video_coding/codecs/test/videoprocessor.cc
diff --git a/webrtc/modules/video_coding/codecs/test/videoprocessor.cc b/webrtc/modules/video_coding/codecs/test/videoprocessor.cc
index aaf29ebb9e1ff2121ddd9a58c5d9e105a83e41e6..63f0a871503cf700bcf09f7d06425de09215c0d5 100644
--- a/webrtc/modules/video_coding/codecs/test/videoprocessor.cc
+++ b/webrtc/modules/video_coding/codecs/test/videoprocessor.cc
@@ -385,9 +385,9 @@ void VideoProcessorImpl::FrameDecoded(const VideoFrame& image) {
 
 int VideoProcessorImpl::GetElapsedTimeMicroseconds(int64_t start,
                                                    int64_t stop) {
-  uint64_t encode_time = (stop - start) / rtc::kNumNanosecsPerMicrosec;
-  RTC_DCHECK_LT(encode_time,
-                static_cast<unsigned int>(std::numeric_limits<int>::max()));
+  int64_t encode_time = (stop - start) / rtc::kNumNanosecsPerMicrosec;
+  RTC_DCHECK_GE(encode_time, std::numeric_limits<int>::min());
+  RTC_DCHECK_LE(encode_time, std::numeric_limits<int>::max());
   return static_cast<int>(encode_time);
 }