Added new histogram for analyzing SDCH corruption detection cases.

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 57cf2870374239a36267d9e56c954da44c72c716..d9082debd3296df2f9727fa4a1fec4f9e2d30d83 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -28608,6 +28608,28 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Each sample is the report of a distinct problem code.</summary>
 </histogram>
 
+<histogram name="Sdch3.ResponseCorruptionDetectionCached"

[Alexei Svitkine (slow), 2014/09/09 18:12:01]

Nit: I'd rename this (and the corresponding C++) to
Sdch3.ResponseCorruptionDetection.Cached (and the one below to
Sdch3.ResponseCorruptionDetection.Uncached). This will provide better grouping
on the dashboard.

[Randy Smith (Not in Mondays), 2014/09/09 18:27:06]

Good idea; thank you.  Done.

+    enum="SdchResponseCorruptionDetectionCauses">
+  <owner>rdsmith@chromium.org</owner>
+  <summary>
+    Attempted SDCH decoding can fail at the Read() filter processing stage.  In
+    some of those cases, the request is corrupted enough that it must be either
+    retried or failed completely.  This histogram records the details of why the
+    request was considered corrupted, for results returned from the cache.
+  </summary>
+</histogram>
+
+<histogram name="Sdch3.ResponseCorruptionDetectionUncached"
+    enum="SdchResponseCorruptionDetectionCauses">
+  <owner>rdsmith@chromium.org</owner>
+  <summary>
+    Attempted SDCH decoding can fail at the Read() filter processing stage.  In
+    some of those cases, the request is corrupted enough that it must be either
+    retried or failed completely.  This histogram records the details of why the
+    request was considered corrupted for results returned from the network.
+  </summary>
+</histogram>
+
 <histogram name="Sdch3.UnflushedBufferSize" units="bytes">
   <owner>rdsmith@chromium.org</owner>
   <summary>
@@ -49178,6 +49200,20 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="100" label="LATENCY_TEST_DISALLOWED"/>
 </enum>
 
+<enum name="SdchResponseCorruptionDetectionCauses" type="int">
+  <summary>
+    SDCH decode corruption detection cases, listed in net/filter/sdch_filter.cc.
+    See also comments in SdchFilter::ReadFilteredData in the same file.
+  </summary>
+  <int value="1" label="RESPONSE_404"/>
+  <int value="2" label="RESPONSE_NOT_200"/>
+  <int value="3" label="RESPONSE_OLD_UNENCODED"/>
+  <int value="4" label="RESPONSE_TENTATIVE_SDCH"/>
+  <int value="5" label="RESPONSE_NO_DICTIONARY"/>
+  <int value="6" label="RESPONSE_CORRUPT_SDCH"/>
+  <int value="7" label="RESPONSE_ENCODING_LIE"/>
+</enum>
+
 <enum name="SearchAccessPoint" type="int">
   <int value="0" label="Omnibox"/>
   <int value="1" label="Omnibox Instant"/>