Make DataUseTabModel and DataUseMatcher more independent

chrome/browser/android/data_usage/external_data_use_observer.cc

Index: chrome/browser/android/data_usage/external_data_use_observer.cc
diff --git a/chrome/browser/android/data_usage/external_data_use_observer.cc b/chrome/browser/android/data_usage/external_data_use_observer.cc
index 36d3c860696f824c193bcb56a3c77f97804bc704..02b5fd06603ff5834792b53291363048d571d135 100644
--- a/chrome/browser/android/data_usage/external_data_use_observer.cc
+++ b/chrome/browser/android/data_usage/external_data_use_observer.cc
@@ -6,6 +6,8 @@
 
 #include <utility>
 
+#include "base/bind.h"
+#include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
@@ -133,7 +135,12 @@ ExternalDataUseObserver::ExternalDataUseObserver(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner)
     : data_use_aggregator_(data_use_aggregator),
       external_data_use_observer_bridge_(new ExternalDataUseObserverBridge()),
-      data_use_tab_model_(new DataUseTabModel()),
+      data_use_tab_model_(new DataUseTabModel(
+          base::Bind(&ExternalDataUseObserverBridge::FetchMatchingRules,
+                     base::Unretained(external_data_use_observer_bridge_)),

[tbansal1, 2016/07/18 17:04:38]

Add comment about why it is okay to use base::Unretained here. Essentially show
that the bridge is guaranteed to be non-null anytime this callback is run.

Same below.

[Raj, 2016/07/19 00:19:02]

Done.

+          base::Bind(
+              &ExternalDataUseObserverBridge::ShouldRegisterAsDataUseObserver,
+              base::Unretained(external_data_use_observer_bridge_)))),
       last_data_report_submitted_ticks_(base::TimeTicks()),
       pending_report_bytes_(0),
       ui_task_runner_(ui_task_runner),
@@ -160,8 +167,7 @@ ExternalDataUseObserver::ExternalDataUseObserver(
 
   ui_task_runner_->PostTask(FROM_HERE,
                             base::Bind(&DataUseTabModel::InitOnUIThread,

[tbansal1, 2016/07/18 17:04:38]

Is it possible that this initialization calls the bridge callback when bridge is
not initialized?

[Raj, 2016/07/19 00:19:02]

Removed this. InitOnUIThread() is not needed.

-                                       base::Unretained(data_use_tab_model_),
-                                       external_data_use_observer_bridge_));
+                                       base::Unretained(data_use_tab_model_)));
 
   // Initialize the ExternalDataUseObserverBridge object. It is okay to use
   // base::Unretained here since |external_data_use_observer_bridge_| is owned