[Sync] Finch Experiment : Enable compression between sync client and server

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 3a0a58f7f3e3649b84e6a8f45484945da54be3fa..beb9945d3952e85f961e308241192813d9efe085 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -44643,12 +44643,44 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Sync.RequestContentLengthCompressed" units="byte">
+  <owner>gangwu@chromium.org</owner>
+  <summary>
+    The request content size for a single HTTP/HTTPS call from sync client to
+    server. The content is compressed by gzip.
+  </summary>
+</histogram>
+
+<histogram name="Sync.RequestContentLengthOriginal" units="byte">
+  <owner>gangwu@chromium.org</owner>
+  <summary>
+    The original request content size for a single HTTP/HTTPS call from sync
+    client to server. It is the size before content got compressed.
+  </summary>
+</histogram>
+
 <histogram name="Sync.ResolveSimpleConflict"
     enum="SyncSimpleConflictResolutions">
   <owner>zea@chromium.org</owner>
   <summary>Enumeration of types of simple conflict resolutions.</summary>
 </histogram>
 
+<histogram name="Sync.ResponseContentLengthCompressed" units="byte">
+  <owner>gangwu@chromium.org</owner>
+  <summary>
+    The response content size for a single HTTP/HTTPS call from sync server to
+    client. The content is compressed by gzip.
+  </summary>
+</histogram>
+
+<histogram name="Sync.ResponseContentLengthOriginal" units="byte">
+  <owner>gangwu@chromium.org</owner>
+  <summary>
+    The original response content size for a single HTTP/HTTPS call from sync
+    server and client. It is the size after content got uncompressed.
+  </summary>
+</histogram>
+
 <histogram name="Sync.RestoreBackendInitializeSucess" enum="BooleanSuccess">
   <obsolete>
     Deprecated 11/2011.  Was counted incorrectly.  Replaced by