Actually update FieldTrialEntry's activated field

base/metrics/field_trial.h

Index: base/metrics/field_trial.h
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index e975150cba38378a14c9224636d020cb5ea7a767..30b057da4069a37b25ea7fafd92f3344d62c385b 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -269,8 +269,7 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   // Adds the field trial to the allocator whose memory is to be shared with
   // child processes. Assumes the calling code has a lock around the call to
   // this function, since the check for the allocator is not thread-safe.
-  void AddToAllocatorWhileLocked(
-      base::SharedPersistentMemoryAllocator* allocator);
+  void AddToAllocatorWhileLocked(SharedPersistentMemoryAllocator* allocator);
 
   // Returns the group_name. A winner need not have been chosen.
   std::string group_name_internal() const { return group_name_; }
@@ -323,6 +322,9 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   // group.
   static bool enable_benchmarking_;
 
+  // Reference to related field trial struct and data in shared memory.
+  SharedPersistentMemoryAllocator::Reference ref_;

[Alexei Svitkine (slow), 2016/10/25 19:18:53]

Nit: Move this above the static var above - so all the non-static members are
together.

[lawrencewu, 2016/10/25 20:27:33]

Done.

+
   DISALLOW_COPY_AND_ASSIGN(FieldTrial);
 };
 
@@ -526,6 +528,9 @@ class BASE_EXPORT FieldTrialList {
   // Return the number of active field trials.
   static size_t GetFieldTrialCount();
 
+  // Return the field trial allocator (for adding to it).
+  static SharedPersistentMemoryAllocator* GetFieldTrialAllocator();
+
  private:
   // Allow tests to access our innards for testing purposes.
   FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator);
@@ -583,8 +588,8 @@ class BASE_EXPORT FieldTrialList {
   // Allocator used to instantiate field trial in child processes. In the
   // future, we may want to move this to a more generic place if we want to
   // start passing more data other than field trials.
-  std::unique_ptr<base::SharedPersistentMemoryAllocator>
-      field_trial_allocator_ = nullptr;
+  std::unique_ptr<SharedPersistentMemoryAllocator> field_trial_allocator_ =
+      nullptr;
 
 #if defined(OS_WIN)
   // Readonly copy of the handle to the allocator. Needs to be a member variable