Fix a race condition in preference metric reporting.

base/prefs/json_pref_store.h

Index: base/prefs/json_pref_store.h
diff --git a/base/prefs/json_pref_store.h b/base/prefs/json_pref_store.h
index 9e6c1821834e712496f6cf481fc501a56bbfab30..d6fbfc00103164009faf6689479e31cddfe9a48d 100644
--- a/base/prefs/json_pref_store.h
+++ b/base/prefs/json_pref_store.h
@@ -18,6 +18,8 @@
 #include "base/prefs/base_prefs_export.h"
 #include "base/prefs/persistent_pref_store.h"
 
+class PrefFilter;

[gab, 2013/12/06 17:23:38]

Don't you need the full type here since you declare a scoped_ptr to one below?
Or is it sufficient that the full type only exist where the destructor is
defined?

[erikwright (departed), 2013/12/06 19:00:47]

The latter. It's the call to scoped_ptr<T>::~scoped_ptr<T>() that instantiates
the method definition, and it's the instantiation of the method definition that
calls T::~T() (and thus needs to know if it is virtual). And it's
JsonPrefStore::~JsonPrefStore() that implicitly includes the calls to the
destructors of all JsonPrefStore members.

Since the latter occurs in the .cc file, all the other stuff also implicitly
occurs there.

+
 namespace base {
 class DictionaryValue;
 class FilePath;
@@ -41,7 +43,8 @@ class BASE_PREFS_EXPORT JsonPrefStore
   // |sequenced_task_runner| is must be a shutdown-blocking task runner, ideally
   // created by GetTaskRunnerForFile() method above.
   JsonPrefStore(const base::FilePath& pref_filename,
-                base::SequencedTaskRunner* sequenced_task_runner);
+                base::SequencedTaskRunner* sequenced_task_runner,
+                scoped_ptr<PrefFilter> pref_filter);
 
   // PrefStore overrides:
   virtual bool GetValue(const std::string& key,
@@ -88,6 +91,7 @@ class BASE_PREFS_EXPORT JsonPrefStore
   // Helper for safely writing pref data.
   base::ImportantFileWriter writer_;
 
+  scoped_ptr<PrefFilter> pref_filter_;
   ObserverList<PrefStore::Observer, true> observers_;
 
   scoped_ptr<ReadErrorDelegate> error_delegate_;