Add DataReductionProxyExperimentsStats and UMA for measuring potentially non-compressed bytes.

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 19141d7359be933da1bf2f07eb78c1ea9bd0d2fd..6f8708f5c5939697be2706ac8b4b140a7d55eea7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4298,6 +4298,41 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="DataReductionProxy.ConfigFetchLostBytesCL">
+  <owner>jeremyim@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    Size of the response body. This is the actual number of bytes received,
+    which usually agrees with but is not necessarily the same as the size
+    specified by the Content-Length header. Only recorded if the request is sent
+    while a simulated Data Reduction Proxy configuration fetch is taking place.
+  </summary>
+</histogram>
+
+<histogram name="DataReductionProxy.ConfigFetchLostBytesDiff">
+  <owner>jeremyim@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    The difference between the size specified in the X-Original-Content-Length
+    header and the size of the response body. Only recorded if the request is
+    sent while a simulated Data Reduction Proxy configuration fetch is taking
+    place. Only positive values are logged, so if X-Original-Content-Length is
+    not specified or if it equals or exceeds the content length, it is not
+    logged.
+  </summary>
+</histogram>
+
+<histogram name="DataReductionProxy.ConfigFetchLostBytesOCL">
+  <owner>jeremyim@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    Size specified in the X-Original-Content-Length header. If this header is
+    not present in the response, the size of the response body is used. Only
+    recorded if the request is sent while a simulated Data Reduction Proxy
+    configuration fetch is taking place.
+  </summary>
+</histogram>
+
 <histogram
     name="DataReductionProxy.ConfigService.FetchFailedAttemptsBeforeSuccess">
   <owner>jeremyim@chromium.org</owner>
@@ -66606,6 +66641,22 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="DataReductionProxy.BypassedBytes"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="DataReductionProxyConfigFetchLostBytes" separator="_">
+  <suffix name="0" label="Bucket 0 for gathering multiple data points."/>
+  <suffix name="1" label="Bucket 1 for gathering multiple data points."/>
+  <suffix name="2" label="Bucket 2 for gathering multiple data points."/>
+  <suffix name="3" label="Bucket 3 for gathering multiple data points."/>
+  <suffix name="4" label="Bucket 4 for gathering multiple data points."/>
+  <suffix name="5" label="Bucket 5 for gathering multiple data points."/>
+  <suffix name="6" label="Bucket 6 for gathering multiple data points."/>
+  <suffix name="7" label="Bucket 7 for gathering multiple data points."/>
+  <suffix name="8" label="Bucket 8 for gathering multiple data points."/>
+  <suffix name="9" label="Bucket 9 for gathering multiple data points."/>
+  <affected-histogram name="DataReductionProxy.ConfigFetchLostBytesCL"/>
+  <affected-histogram name="DataReductionProxy.ConfigFetchLostBytesDiff"/>
+  <affected-histogram name="DataReductionProxy.ConfigFetchLostBytesOCL"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="DataReductionProxyMissingViaHeaderBytes"
     separator=".">
   <suffix name="4xx" label="Response with 4xx response code"/>