Consolidate some safe-browsing histograms.

chrome/browser/safe_browsing/protocol_manager.h

Index: chrome/browser/safe_browsing/protocol_manager.h
diff --git a/chrome/browser/safe_browsing/protocol_manager.h b/chrome/browser/safe_browsing/protocol_manager.h
index 7869e0f4ac666ec836f2a837f6b4af0d7b0f922c..0ef766a0dab85311731181403c098c8f8b106a41 100644
--- a/chrome/browser/safe_browsing/protocol_manager.h
+++ b/chrome/browser/safe_browsing/protocol_manager.h
@@ -158,6 +158,31 @@ class SafeBrowsingProtocolManager : public URLFetcher::Delegate {
     return additional_query_;
   }
 
+  // Enumerate failures for histogramming purposes.  DO NOT CHANGE THE
+  // ORDERING OF THESE VALUES.
+  enum ResultType {
+    // A 204 response code means that the server did not know about
+    // the hash prefix that was sent up.
+    GET_HASH_STATUS_200,
+    GET_HASH_STATUS_204,
+
+    // Responses which returned no full hashes.  This includes the 204
+    // case, and also 200 responses for prefixes which are logically

[Erik does not do reviews, 2010/12/22 22:07:22]

So should we split these up?  GET_HASH_FULL_HASH_EMPTY_200/204?  Without them
being split, I'm not sure how you would know what we were getting more of one
than the other.

[Scott Hess - ex-Googler, 2010/12/22 22:13:20]

My understanding is that every GET_HASH_STATUS_204 should be empty (that's what
http status code 204 means), so that shouldn't add any info about what is
already here.  Would it?

[lzheng, 2010/12/22 23:56:51]

That's my understanding too. So, GET_HASH_FULL_HASH_EMPTY = (GET_HASH_STATUS_200
- GET_HASH_FULL_HASH_HIT) + GET_HASH_STATUS_204. I think you could export
(GET_HASH_STATUS_200 - GET_HASH_FULL_HASH_HIT) too (what's Erik wants, I
believe), but since it could be calculated out, I am fine either way.

+    // deleted at the server but not yet updated to the client.
+    GET_HASH_FULL_HASH_EMPTY,
+
+    // Subset of 200 responses for which one or more of the full
+    // hashes matched.
+    GET_HASH_FULL_HASH_HIT,
+
+    // Memory space for histograms is determined by the max.  ALWAYS
+    // ADD NEW VALUES BEFORE THIS ONE.
+    GET_HASH_RESULT_MAX
+  };
+
+  // Record a GetHash result.
+  static void RecordGetHashResult(ResultType result_type);
+
  protected:
   // Constructs a SafeBrowsingProtocolManager for |sb_service| that issues
   // network requests using |request_context_getter|. When |disable_auto_update|