Notify DataUseTabModel of navigations and tab closures

chrome/browser/android/data_usage/external_data_use_observer.h

Index: chrome/browser/android/data_usage/external_data_use_observer.h
diff --git a/chrome/browser/android/data_usage/external_data_use_observer.h b/chrome/browser/android/data_usage/external_data_use_observer.h
index 1a2b5b29d9749dd0f05428877b5b31839a99f8f9..470e033df462b4b76400b5190215f0a5cfa1b948 100644
--- a/chrome/browser/android/data_usage/external_data_use_observer.h
+++ b/chrome/browser/android/data_usage/external_data_use_observer.h
@@ -96,29 +96,30 @@ class ExternalDataUseObserver : public data_usage::DataUseAggregator::Observer {
   bool MatchesAppPackageName(const std::string& app_package_name,
                              std::string* label) const;
 
-  DataUseTabModel* data_use_tab_model() const {
-    return data_use_tab_model_.get();
+  const base::WeakPtr<DataUseTabModel>& data_use_tab_model_weak_ptr() const {

[sclittle, 2015/11/23 23:06:16]

nit: Why can't this just be as it was before? Or make this a non-const method
and name it data_use_tab_model() and return data_use_tab_model_->GetWeakPtr()?
You'd want to move the implementation to the .cc file and add a thread_checker_
check.

[tbansal1, 2015/11/24 00:42:03]

weak ptr has to be generated on IO thread,  stored somewhere where it is
accessible on UI thread for consumption by profile_impl_io_data*. The weakptr
can't be stored in IOThread::Globals() because globals are not accessible on UI
thread. Also, it has to be generated before it is consumed by
profile_impl_io_data* because profile_impl_io_data* runs on UI thread.

If I change it to "return data_use_tab_model_->GetWeakPtr()?", it is not clear
where this function would be called, and where the weak ptr would be stored.

[sclittle, 2015/11/24 04:11:50]

I'm confused - this method is run on the IO thread, right? If so, then
data_use_tab_model_->GetWeakPtr() is just as safe to run, right?

+    return data_use_tab_model_weak_ptr_;
   }
 
  private:
   friend class DataUseTabModelTest;
   friend class ExternalDataUseObserverTest;
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, SingleRegex);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, TwoRegex);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, MultipleRegex);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, ChangeRegex);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, LabelRemoved);
   FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest,
                            AtMostOneDataUseSubmitRequest);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, BufferDataUseReports);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, BufferSize);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, ChangeRegex);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, HashFunction);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, LabelRemoved);
   FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, MultipleMatchingRules);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, MultipleRegex);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest,
+                           PeriodicFetchMatchingRules);
   FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, ReportsMergedCorrectly);
+  FRIEND_TEST_ALL_PREFIXES(DataUseUITabModelTest, ReportTabEventsTest);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, SingleRegex);
   FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest,
                            TimestampsMergedCorrectly);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, HashFunction);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, BufferSize);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest,
-                           PeriodicFetchMatchingRules);
-  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, BufferDataUseReports);
+  FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, TwoRegex);
   FRIEND_TEST_ALL_PREFIXES(ExternalDataUseObserverTest, Variations);
 
   // DataUseReportKey is a unique identifier for a data use report.
@@ -277,6 +278,7 @@ class ExternalDataUseObserver : public data_usage::DataUseAggregator::Observer {
 
   // Maintains tab sessions.
   scoped_ptr<DataUseTabModel> data_use_tab_model_;
+  base::WeakPtr<DataUseTabModel> data_use_tab_model_weak_ptr_;
 
   // True if callback from |FetchMatchingRulesDone| is currently pending.
   bool matching_rules_fetch_pending_;