Add detailed histograms for DownloadProtectionService URLFetcher errors.

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 d224471e86ff4a09869d769d38fd679c6bfb8316..b40f7abd5057065c450531d07abb74b9ccb21937 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -12393,6 +12393,29 @@ other types of suffix sets.
   <summary>The number of chunk URLs in an update response.</summary>
 </histogram>
 
+<histogram name="SBClientDownload.CheckDownloadRequestNetError"

[mmenke, 2013/07/24 14:26:50]

nit:  Think the "Check" isn't needed.  This is a histogram of just the
DownloadRequestNetError codes.  Check doesn't seem to add anything.  Or it is
just for sorting purposes?

[mattm, 2013/07/24 22:39:27]

Mostly it was to sort it near the CheckDownloadStats histogram, but I see there
is also a DownloadRequestDuration histogram, so I guess the shorter form would
be fine too.

+    enum="NetErrorCodes">
+  <summary>
+    For CheckClientDownloadRequest URLFetchers with failed status, the net error
+    code.
+  </summary>
+</histogram>
+
+<histogram name="SBClientDownload.CheckDownloadRequestResponseCode">
+  <summary>
+    For CheckClientDownloadRequest URLFetchers with successful status, the HTTP
+    response code that was received.
+  </summary>
+</histogram>
+
+<histogram name="SBClientDownload.CheckDownloadRequestStatus"
+    enum="URLRequestStatus">
+  <summary>
+    The URLRequestStatus value for CheckClientDownloadRequest URLFetcher
+    completion.
+  </summary>
+</histogram>
+
 <histogram name="SBClientDownload.CheckDownloadStats"
     enum="SBClientDownloadCheckDownloadStats">
   <summary>
@@ -21204,6 +21227,13 @@ other types of suffix sets.
   <int value="42" label="kErrorCodeUpdateCanceledByChannelChange"/>
 </enum>
 
+<enum name="URLRequestStatus" type="int">
+  <int value="0" label="SUCCESS"/>
+  <int value="1" label="IO_PENDING"/>
+  <int value="2" label="CANCELLED"/>
+  <int value="3" label="FAILED"/>
+</enum>
+
 <enum name="UrlResolutionResult" type="int">
   <int value="0" label="Absolute URL"/>
   <int value="1" label="Resolutions Differ"/>