Notify DataUseTabModel of navigations and tab closures

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index f57bc395a0eb16e6b0e6966ac96c5461a152ea8d..bc8ac3c3f6f53bda27606568105d044aa667049e 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -39,6 +39,7 @@ class CommandLine;
 #if defined(OS_ANDROID)
 namespace chrome {
 namespace android {
+class DataUseTabModel;
 class ExternalDataUseObserver;
 }
 }
@@ -270,6 +271,9 @@ class IOThread : public content::BrowserThreadDelegate {
 chrome::android::ExternalDataUseObserver* external_data_use_observer() const {

[mmenke, 2015/11/17 22:48:40]

nit:  Both of these methods should be indented 2.

[tbansal1, 2015/11/18 01:32:24]

Done.

   return external_data_use_observer_.get();
 }

[mmenke, 2015/11/17 22:48:40]

nit:  Blank line between methods

[tbansal1, 2015/11/18 01:32:24]

Done.

+base::WeakPtr<chrome::android::DataUseTabModel> data_use_tab_model() const {

[mmenke, 2015/11/17 22:48:40]

Hrm...actually, do we even need a weak pointer here?  The IOThread class is
called the IOThread for a reason.  Even ignoring that, as long as there's a
profile on the UI thread, the corresponding stuff will still exist on the
IOThread when a task is posted there.

Seems like we could just get rid of the accessor entirely, and have the consumer
get the data_use_tab_model from the IOThread's external_data_use_observer
directly.

More generally, exposing weak pointers widely obscures lifetimes, and is
generally considered a bit of an anti-pattern.

[tbansal1, 2015/11/18 01:32:24]

But there could be a function on DataUseTabModel posted from UI thread on IO
thread. In that case, it is possible that profile is destroyed on UI thread, but
the function with raw pointer is still pending. So, it seems that we need to
have a weak pointer to DataUseTabModel which is generated on IO thread.

+  return data_use_tab_model_;
+}
 #endif  // defined(OS_ANDROID)
 
  private:
@@ -539,6 +543,8 @@ chrome::android::ExternalDataUseObserver* external_data_use_observer() const {
 #if defined(OS_ANDROID)
   scoped_ptr<chrome::android::ExternalDataUseObserver>
       external_data_use_observer_;
+  // WeakPtr to DataUseTabModel to be used on IO thread.
+  base::WeakPtr<chrome::android::DataUseTabModel> data_use_tab_model_;
 #endif  // defined(OS_ANDROID)
 
   const base::TimeTicks creation_time_;