Handle zero timestamp in RTCVideoEncoder timestamp matching & add UMA

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index d49de6ca46708540be8ead92b5e64157f34035de..5b3a6a41b4a82a55b60f9be00cd226125be454b7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -29552,6 +29552,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Video codec profile used in RTC video encoder.</summary>
 </histogram>
 
+<histogram name="Media.RTCVideoEncoderTimestampMatchSuccess"
+    enum="BooleanSuccess">
+  <owner>emircan@chromium.org</owner>
+  <summary>
+    Indicates whether we were successful in preserving timestamps in hardware
+    video encoder session. It is tracked during the session and logged after it
+    ends.
+  </summary>
+</histogram>
+
 <histogram name="Media.Session.ActiveTime" units="ms">
   <owner>avayvod@chromium.org</owner>
   <owner>mlamouri@chromium.org</owner>
@@ -76339,8 +76349,8 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>treib@chromium.org</owner>
   <summary>
     The time for the new tab page to fire the &quot;load&quot; event. Note: This
-    is usually recorded with a suffix (.Local/Google/Other). The base version
-    is recorded only on Android. Recorded only once per tab, i.e. excluding
+    is usually recorded with a suffix (.Local/Google/Other). The base version is
+    recorded only on Android. Recorded only once per tab, i.e. excluding
     back/forward navigations.
   </summary>
 </histogram>