Update from https://crrev.com/327068

base/prefs/pref_registry.h

Index: base/prefs/pref_registry.h
diff --git a/base/prefs/pref_registry.h b/base/prefs/pref_registry.h
index a500b6e691a08e73a0be65651da892edaf86aec7..cc5804ef10a9d2e713be2dc9c50d205219f34c04 100644
--- a/base/prefs/pref_registry.h
+++ b/base/prefs/pref_registry.h
@@ -5,6 +5,7 @@
 #ifndef BASE_PREFS_PREF_REGISTRY_H_
 #define BASE_PREFS_PREF_REGISTRY_H_
 
+#include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/prefs/base_prefs_export.h"
 #include "base/prefs/pref_value_map.h"
@@ -27,10 +28,26 @@ class PrefStore;
 // also work, but this is being deprecated.
 class BASE_PREFS_EXPORT PrefRegistry : public base::RefCounted<PrefRegistry> {
  public:
+  // Registration flags that can be specified which impact how the pref will
+  // behave or be stored. This will be passed in a bitmask when the pref is
+  // registered. Subclasses of PrefRegistry can specify their own flags. Care
+  // must be taken to ensure none of these overlap with the flags below.
+  enum PrefRegistrationFlags {
+    // No flags are specified.
+    NO_REGISTRATION_FLAGS = 0,
+
+    // The first 8 bits are reserved for subclasses of PrefRegistry to use.
+  };
+
   typedef PrefValueMap::const_iterator const_iterator;
+  typedef base::hash_map<std::string, uint32> PrefRegistrationFlagsMap;
 
   PrefRegistry();
 
+  // Retrieve the set of registration flags for the given preference. The return
+  // value is a bitmask of PrefRegistrationFlags.
+  uint32 GetRegistrationFlags(const std::string& pref_name) const;
+
   // Gets the registered defaults.
   scoped_refptr<PrefStore> defaults();
 
@@ -47,11 +64,17 @@ class BASE_PREFS_EXPORT PrefRegistry : public base::RefCounted<PrefRegistry> {
   friend class base::RefCounted<PrefRegistry>;
   virtual ~PrefRegistry();
 
-  // Used by subclasses to register a default value for a preference.
-  void RegisterPreference(const std::string& path, base::Value* default_value);
+  // Used by subclasses to register a default value and registration flags for
+  // a preference. |flags| is a bitmask of |PrefRegistrationFlags|.
+  void RegisterPreference(const std::string& path,
+                          base::Value* default_value,
+                          uint32 flags);
 
   scoped_refptr<DefaultPrefStore> defaults_;
 
+  // A map of pref name to a bitmask of PrefRegistrationFlags.
+  PrefRegistrationFlagsMap registration_flags_;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(PrefRegistry);
 };