Add metrics for tracking UX impact of non-static CLD data providers

chrome/renderer/translate/translate_helper.h

Index: chrome/renderer/translate/translate_helper.h
diff --git a/chrome/renderer/translate/translate_helper.h b/chrome/renderer/translate/translate_helper.h
index 1c357bf9e606308f1a6f2d9ff8fc487733b2c55e..a4530c4ad3aff6e1e54192e8f545d6eaa737b029 100644
--- a/chrome/renderer/translate/translate_helper.h
+++ b/chrome/renderer/translate/translate_helper.h
@@ -113,6 +113,13 @@ class TranslateHelper : public content::RenderViewObserver {
   FRIEND_TEST_ALL_PREFIXES(TranslateHelperTest, SimilarLanguageCode);
   FRIEND_TEST_ALL_PREFIXES(TranslateHelperTest, WellKnownWrongConfiguration);
 
+  enum LanguageDetectionTiming {
+    ON_TIME,   // Language detection was performed as soon as it was requested
+    DEFERRED,  // Language detection couldn't be performed when it was requested
+    RESUMED,   // A deferred language detection attempt was completed later
+    kLanguageDetectionTimingMax  // bounding value for this enum

[Alexei Svitkine (slow), 2014/07/16 14:50:40]

Nit: Use same naming convention as for the other enum members.

[andrewhayden, 2014/07/17 08:36:19]

This is copied from the same place the rest of this approach came from, but I
have no qualms about changing it.

+  };
+
   // Converts language code to the one used in server supporting list.
   static void ConvertLanguageCodeSynonym(std::string* code);
 
@@ -167,6 +174,11 @@ class TranslateHelper : public content::RenderViewObserver {
   // Callback triggered when CLD data becomes available.
   void OnCldDataAvailable();
 
+  // Record the timing of language detection, immediately sending an IPC-based

[jar (doing other things), 2014/07/16 16:44:44]

nit: perhaps better would be to aggregate these requests, so that you can rate
limit how often this fires.

For instance, you could rate limit by posting a delayed task, and having a bool
that indicates that there is already a task pending.

Without this, you'll be doing a lot of work (scanning all histograms in the
renderer!) each time you do a minor update in your histogram :-(.

It might even be interesting to put such functionality into the histogram system
itself, in case other folks want to fire such updates "RSN".

[andrewhayden, 2014/07/17 08:36:19]

Totally agree, but again very far out of scope for what should be a trivial
addition to the code here. I don't expect this to fire more than once per page
load in the VAST (>99%) majority of use cases.

+  // histogram delta update to the browser process in case the hosting renderer
+  // process terminates before the metrics would otherwise be transferred.
+  void RecordLanguageDetectionTiming(LanguageDetectionTiming);
+
   // An ever-increasing sequence number of the current page, used to match up
   // translation requests with responses.
   int page_seq_no_;