Reject unadvertised encodings

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 21f1ae8975fb61db1c74a2a900910d8e28b7c134..fa1b40e4f56b690512236ae8c7afcb38b35bffac 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -32184,6 +32184,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.ContentDecodingRejected.FilterType" enum="NetFilterType2">

[Randy Smith (Not in Mondays), 2017/03/28 19:55:36]

Just to get it all in one place, my recommendation/request around histograms is:
* No new histogram; keep using ContentDecodingFailed.
* Two new enum entries: Unknown  (optional; feel free to leave it to me) +
Rejected.
* Unknown is returned from URLRequestHttpJob::SetUpSourceStream, would not
modify the current behavior of passing through the data,  and would have a
documentation note in the histograms.xml file that it did *not* correspond to an
error of CONTENT_DECODING_FAILED.
* Rejected would be returned from HttpNetworkTransaction for any rejected
content encoding.
* All entries for the histogram would be done through a static function on
FilterSourceStream (as current; I'm just advocating for switching to the old
histogram).

+  <owner>xunjieli@chromium.org</owner>
+  <summary>
+    For each CONTENT_DECODING_FAILED, raised by network transaction.
+  </summary>
+</histogram>
+
 <histogram name="net.CookieBackingStoreUpdateResults"
     enum="BackingStoreResults">
   <obsolete>
@@ -102608,6 +102615,7 @@ from previous Chrome versions.
   <int value="5" label="SDCHPossible"/>
   <int value="6" label="Invalid"/>
   <int value="7" label="None"/>
+  <int value="8" label="Unknown"/>
 </enum>
 
 <enum name="NetInternalsUiFeature" type="int">