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diff --git a/base/trace_event/category_registry.h b/base/trace_event/category_registry.h
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+++ b/base/trace_event/category_registry.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_
+#define BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/base_export.h"
+#include "base/logging.h"
+
+namespace base {
+namespace trace_event {
+
+struct TraceCategory;
+class TraceCategoryTest;
+class TraceLog;
+
+// Allows fast and thread-safe acces to the state of all tracing categories.
+// All the methods in this class can be concurrently called on multiple threads,
+// unless otherwise noted (e.g., GetOrCreateCategoryLocked).
+// The reason why this is a fully static class with global state is to allow to
+// statically define known categories as global linker-initialized structs,
+// without requiring static initializers.
+class BASE_EXPORT CategoryRegistry {
+ public:
+  // Allows for-each iterations over a slice of the categories array.
+  class Range {
+   public:
+    Range(TraceCategory* begin, TraceCategory* end) : begin_(begin), end_(end) {
+      DCHECK_LE(begin, end);
+    }
+    TraceCategory* begin() const { return begin_; }
+    TraceCategory* end() const { return end_; }
+
+   private:
+    TraceCategory* const begin_;
+    TraceCategory* const end_;
+  };
+
+  // Known categories.
+  static TraceCategory* const kCategoryExhausted;
+  static TraceCategory* const kCategoryMetadata;
+  static TraceCategory* const kCategoryAlreadyShutdown;
+
+  // Returns a category entry from the Category.state_ptr() pointer.
+  // TODO(primiano): trace macros should just keep a pointer to the entire
+  // TraceCategory, not just the enabled state pointer. That would remove the
+  // need for this function and make everything cleaner at no extra cost (as
+  // long as the |state_| is the first field of the struct, which can be
+  // guaranteed via static_assert, see TraceCategory ctor).
+  static const TraceCategory* GetCategoryByStatePtr(
+      const uint8_t* category_state);
+
+  // Returns a category from its name or nullptr if not found.
+  // The output |category| argument is an undefinitely lived pointer to the
+  // TraceCategory owned by the registry. TRACE_EVENTx macros will cache this
+  // pointer and use it for checks in their fast-paths.
+  static TraceCategory* GetCategoryByName(const char* category_name);
+
+  static bool IsBuiltinCategory(const TraceCategory*);
+
+ private:
+  friend class TraceCategoryTest;
+  friend class TraceLog;
+  using CategoryInitializerFn = void (*)(TraceCategory*);
+
+  // Only for debugging/testing purposes, is a no-op on release builds.
+  static void Initialize();
+
+  // Resets the state of all categories, to clear up the state between tests.
+  static void ResetForTesting();
+
+  // Used to get/create a category in the slow-path. If the category exists
+  // already, this has the same effect of GetCategoryByName and returns false.
+  // If not, a new category is created and the CategoryInitializerFn is invoked
+  // before retuning true. The caller must guarantee serialization: either call
+  // this method from a single thread or hold a lock when calling this.
+  static bool GetOrCreateCategoryLocked(const char* category_name,
+                                        CategoryInitializerFn,
+                                        TraceCategory**);
+
+  // Allows to iterate over the valid categories in a for-each loop.
+  // This includes builtin categories such as __metadata.
+  static Range GetAllCategories();
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_