Implement client side logging for language detection.

chrome/browser/translate/chrome_translate_client.cc

Index: chrome/browser/translate/chrome_translate_client.cc
diff --git a/chrome/browser/translate/chrome_translate_client.cc b/chrome/browser/translate/chrome_translate_client.cc
index 830d647c55473048a8813db47a967be9b8bbf6bb..4e88a35169336c8dde76cdecd56674920cd5610a 100644
--- a/chrome/browser/translate/chrome_translate_client.cc
+++ b/chrome/browser/translate/chrome_translate_client.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/translate/chrome_translate_client.h"
 
+#include <memory>
 #include <vector>
 
 #include "base/logging.h"
@@ -14,6 +15,7 @@
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/infobars/infobar_service.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/sync/user_event_service_factory.h"
 #include "chrome/browser/translate/language_model_factory.h"
 #include "chrome/browser/translate/translate_accept_languages_factory.h"
 #include "chrome/browser/translate/translate_ranker_factory.h"
@@ -29,6 +31,8 @@
 #include "chrome/grit/theme_resources.h"
 #include "components/metrics/proto/translate_event.pb.h"
 #include "components/prefs/pref_service.h"
+#include "components/sync/protocol/user_event_specifics.pb.h"
+#include "components/sync/user_events/user_event_service.h"
 #include "components/translate/core/browser/language_model.h"
 #include "components/translate/core/browser/language_state.h"
 #include "components/translate/core/browser/page_translated_details.h"
@@ -39,6 +43,7 @@
 #include "components/translate/core/browser/translate_prefs.h"
 #include "components/translate/core/common/language_detection_details.h"
 #include "components/variations/service/variations_service.h"
+#include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
@@ -65,6 +70,47 @@ metrics::TranslateEventProto::EventType BubbleResultToTranslateEvent(
   }
 }
 
+std::unique_ptr<sync_pb::UserEventSpecifics> ConstructLanguageDetectionEvent(
+    const int entry_id,
+    const translate::LanguageDetectionDetails& details) {
+  auto specifics = base::MakeUnique<sync_pb::UserEventSpecifics>();
+  specifics->set_event_time_usec(base::Time::Now().ToInternalValue());
+
+  // TODO(renjieliu): Revisit this field when the best way to identify
+  // navigations is determined.
+  specifics->set_navigation_id(base::Time::Now().ToInternalValue());

[groby-ooo-7-16, 2017/05/25 21:35:29]

Note: Time::Now() is not guaranteed to be increasing (monotonically or
otherwise) - if that is an issue, you'll need to find another time base.

[napper, 2017/05/25 21:49:26]

See here for the ongoing discussion:
https://docs.google.com/document/d/1ZeMUbFCxUkAlIOzOv4r9eXhLemZH2VR8npfiyXigL...

[renjieliu1, 2017/05/26 00:26:45]

Acknowledged.

[renjieliu1, 2017/05/26 00:26:45]

currently the suggested way is to use time to identify the navigation, we
probably need to change that in future

[groby-ooo-7-16, 2017/05/26 01:28:48]

I'm not sure what your requirements are, so pick what works for you :) Just
pointing out the weirdness of Chrome's time. (BTW: DefaultTickClock is at least
monotonic, and you can mock it for testing. Should you need it)

+
+  sync_pb::LanguageDetection lang_detection;
+  auto* const lang = lang_detection.add_detected_languages();

[groby-ooo-7-16, 2017/05/25 21:35:29]

Wait - isn't this a mutable pointer to a constant lang? I.e. the
set_language_code() calls should fail?

You probably want either auto const*, or better auto*

[napper, 2017/05/25 21:49:26]

Note that the pointer is const (so lang++ won't work) but the object pointed to
by the pointer is non-const (so lang->set_language_code() will work).

[renjieliu1, 2017/05/26 00:26:45]

this is to a const pointer to a mutable object

[renjieliu1, 2017/05/26 00:26:45]

thanks for the clarification! :)

[groby-ooo-7-16, 2017/05/26 01:28:47]

Indeed. Thank you. I can't believe I *still* read them the wrong way around,
even though I know I read them the wrong way around ;)

+  lang->set_language_code(details.cld_language);
+  lang->set_is_reliable(details.is_cld_reliable);
+  // Only set adopted_language when it's different from cld_language.
+  if (details.adopted_language != details.cld_language) {
+    lang_detection.set_adopted_language_code(details.adopted_language);
+  }
+  *specifics->mutable_language_detection() = lang_detection;
+  return specifics;
+}
+
+void LogLanguageDetectionEvent(
+    const content::WebContents* const web_contents,
+    const translate::LanguageDetectionDetails& details) {
+  auto* const profile =
+      Profile::FromBrowserContext(web_contents->GetBrowserContext());
+
+  syncer::UserEventService* const user_event_service =
+      browser_sync::UserEventServiceFactory::GetForProfile(profile);
+
+  const auto* const entry =
+      web_contents->GetController().GetLastCommittedEntry();
+
+  // If entry is null, we don't record the page.

[groby-ooo-7-16, 2017/05/25 21:35:29]

The logic is clear from the code - can you change the comment to explain _why_
we don't record the page on NullPtr? (Also, if we rely on NavigationEntry,
should this be a NavigationObserver?)

[renjieliu1, 2017/05/26 00:26:45]

Added a comment. 

I wonder are you suggesting web_contents_observer:
https://cs.chromium.org/chromium/src/content/public/browser/web_contents_obse...

Currently we're relying on CLD3 to determine the language and Register the
information in the
page(https://cs.chromium.org/chromium/src/components/translate/content/renderer/translate_helper.cc?q=translate_helper&l=132),
thus we can get the language info in
ChromeTranslateClient::OnLanguageDetermined.

[groby-ooo-7-16, 2017/05/26 01:28:48]

No, I meant the NavigationObserver :) It gets notified whenever new
NavigationEntry is created, IIRC. But what you have seems to work fine. 

+  if (entry != nullptr) {
+    user_event_service->RecordUserEvent(
+        ConstructLanguageDetectionEvent(entry->GetUniqueID(), details));
+  }
+}
+
 }  // namespace
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(ChromeTranslateClient);
@@ -309,6 +355,7 @@ void ChromeTranslateClient::OnLanguageDetermined(
       content::Source<content::WebContents>(web_contents()),
       content::Details<const translate::LanguageDetectionDetails>(&details));
 
+  LogLanguageDetectionEvent(web_contents(), details);
   // Unless we have no language model (e.g., in incognito), notify the model
   // about detected language of every page visited.
   if (language_model_ && details.is_cld_reliable)