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..cbfc3b9b5f24f71b54da368ce9bf9637f72058db 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -28211,6 +28211,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Sdch3.CorruptionDetectionCause"
+    enum="SdchCorruptionDetectionCauses">
+  <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.
+  </summary>
+</histogram>
+
 <histogram name="Sdch3.Dictionary size loaded" units="bytes">
   <owner>rdsmith@chromium.org</owner>
   <summary>
@@ -49113,6 +49124,20 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="3" label="SCT_STATUS_OK"/>
 </enum>
 
+<enum name="SdchCorruptionDetectionCauses" type="int">
+  <summary>
+    SDCH decode corruption detection cases, listed in net/filter/sdch_filter.h
+  </summary>
+  <int value="0" label="RESPONSE_200"/>
+  <int value="1" label="RESPONSE_200_CACHED"/>
+  <int value="2" label="TENTATIVE_SDCH"/>
+  <int value="3" label="TENTATIVE_SDCH_CACHED"/>
+  <int value="4" label="DICTIONARY_NOT_FOUND"/>
+  <int value="5" label="DICTIONARY_NOT_FOUND_CACHED"/>
+  <int value="6" label="NON_SDCH_RESPONSE"/>
+  <int value="7" label="NON_SDCH_RESPONSE_CACHED"/>
+</enum>
+
 <enum name="SdchProblemCode" type="int">
   <summary>SDCH problem codes, listed in net/base/sdch_manager.h</summary>
   <int value="1" label="ADDED_CONTENT_ENCODING"/>