Record field-trial information in stability file for crash analysis.

base/debug/activity_tracker.h

Index: base/debug/activity_tracker.h
diff --git a/base/debug/activity_tracker.h b/base/debug/activity_tracker.h
index 2d3c2bc7dbaf3666540cb9e7dda55e179685235a..dadcb5abdd6bddfa5582548ac2261ab52517fbfe 100644
--- a/base/debug/activity_tracker.h
+++ b/base/debug/activity_tracker.h
@@ -26,6 +26,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/location.h"
 #include "base/metrics/persistent_memory_allocator.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_checker.h"
@@ -340,7 +341,7 @@ class BASE_EXPORT ActivityUserData {
   using Snapshot = std::map<std::string, TypedValue>;
 
   ActivityUserData(void* memory, size_t size);
-  ~ActivityUserData();
+  virtual ~ActivityUserData();
 
   // Gets the unique ID number for this user data. If this changes then the
   // contents have been overwritten by another thread. The return value is
@@ -402,6 +403,12 @@ class BASE_EXPORT ActivityUserData {
   // Gets the base memory address used for storing data.
   const void* GetBaseAddress();
 
+ protected:
+  virtual void Set(StringPiece name,
+                   ValueType type,
+                   const void* memory,
+                   size_t size);
+
  private:
   FRIEND_TEST_ALL_PREFIXES(ActivityTrackerTest, UserDataTest);
 
@@ -435,7 +442,6 @@ class BASE_EXPORT ActivityUserData {
     size_t extent;                    // The total storage of the value,
   };                                  // typically rounded up for alignment.
 
-  void Set(StringPiece name, ValueType type, const void* memory, size_t size);
   void SetReference(StringPiece name,
                     ValueType type,
                     const void* memory,
@@ -459,8 +465,6 @@ class BASE_EXPORT ActivityUserData {
   // A pointer to the unique ID for this instance.
   std::atomic<uint32_t>* const id_;
 
-  base::ThreadChecker thread_checker_;
-
   // This ID is used to create unique indentifiers for user data so that it's
   // possible to tell if the information has been overwritten.
   static std::atomic<uint32_t> next_id_;
@@ -780,7 +784,19 @@ class BASE_EXPORT GlobalActivityTracker {
   void RecordModuleInfo(const ModuleInfo& info);
 
   // Accesses the global data record for storing arbitrary key/value pairs.
-  ActivityUserData& user_data() { return user_data_; }
+  ActivityUserData& global_data() { return global_data_; }
+
+  // Record field trial information. This will work even before a global
+  // tracker has been created, holding that information internally until a
+  // global tracker is created at which point everything collected will be
+  // dumped into it. This call is completely thread-safe.

[Alexei Svitkine (slow), 2017/02/07 16:14:06]

Nit: Remove the word "completely". "thread safe" is enough to be clear.

[bcwhite, 2017/02/07 17:39:30]

Done.

+  static void RecordFieldTrial(const std::string& trial_name,
+                               const std::string& group_name);
+
+  // Disable all filed trial recording. This should be called when its known

[Alexei Svitkine (slow), 2017/02/07 16:14:06]

field

[bcwhite, 2017/02/07 17:39:30]

Done.

+  // that no global tracker will be created so as to not hold field-trial
+  // information that will never be collected.
+  static void DisableFieldTrialRecording();
 
  private:
   friend class GlobalActivityAnalyzer;
@@ -795,6 +811,25 @@ class BASE_EXPORT GlobalActivityTracker {
     kCachedUserDataMemories = 10,
   };
 
+  // A wrapper around ActivityUserData that is thread-safe and thus can be used
+  // in the global scope without the requirement of being called from only one
+  // thread.
+  class GlobalUserData : public ActivityUserData {
+   public:
+    GlobalUserData(void* memory, size_t size);
+    ~GlobalUserData() override;
+
+   private:
+    void Set(StringPiece name,
+             ValueType type,
+             const void* memory,
+             size_t size) override;
+
+    Lock data_lock_;
+
+    DISALLOW_COPY_AND_ASSIGN(GlobalUserData);
+  };
+
   // State of a module as stored in persistent memory. This supports a single
   // loading of a module only. If modules are loaded multiple times at
   // different addresses, only the last will be recorded and an unload will
@@ -899,7 +934,7 @@ class BASE_EXPORT GlobalActivityTracker {
 
   // An object for holding global arbitrary key value pairs. Values must always
   // be written from the main UI thread.
-  ActivityUserData user_data_;
+  GlobalUserData global_data_;
 
   // A map of global module information, keyed by module path.
   std::map<const std::string, ModuleInfoRecord*> modules_;