components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/leak_detector_value_type.h

Index: components/metrics/leak_detector/leak_detector_value_type.h
diff --git a/components/metrics/leak_detector/leak_detector_value_type.h b/components/metrics/leak_detector/leak_detector_value_type.h
new file mode 100644
index 0000000000000000000000000000000000000000..5f72b09818769debf7b108bfd744915186942f74
--- /dev/null
+++ b/components/metrics/leak_detector/leak_detector_value_type.h
@@ -0,0 +1,69 @@
+// Copyright 2015 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 COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_VALUE_TYPE_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_VALUE_TYPE_
+
+#include <stddef.h>
+#include <stdint.h>
+
+namespace leak_detector {
+
+// Used for tracking unique call stacks.
+class CallStack;
+
+class LeakDetectorValueType {
+ public:
+  // Supported types.
+  enum Type {
+    kNone,
+    kSize,
+    kCallStack,
+  };
+
+  // Print value type name as singular or plural.
+  enum TypeNameNumber {
+    kSingular,
+    kPlural,
+  };
+
+  LeakDetectorValueType() : type_(kNone) {}
+  explicit LeakDetectorValueType(uint32_t size)
+      : type_(kSize), size_(size) {}
+  explicit LeakDetectorValueType(const CallStack* call_stack)
+      : type_(kCallStack), call_stack_(call_stack) {}

[jar (doing other things), 2015/08/21 02:48:43]

Please initialize all POD members, in both constructors.

[Simon Que, 2015/08/21 21:59:20]

Done.

[Simon Que, 2015/08/23 23:30:53]

I just saw that I hadn't done this completely in a previous patch set. Done.

+
+  // Accessors.
+  Type type() const {
+    return type_;
+  }
+  uint32_t size() const {
+    return size_;
+  }
+  const CallStack* call_stack() const {
+    return call_stack_;
+  }
+
+  // Returns a string containing the word that describes the value type of the
+  // current object. e.g. "size" or "call stack".
+  const char* GetTypeName() const;
+
+  // Writes the current value as a string to |buffer|. Will not write beyond the
+  // buffer size given by |buffer_size|. Returns |buffer| as a const ptr.
+  const char* ToString(char* buffer, size_t buffer_size) const;
+
+  // Comparators.
+  bool operator== (const LeakDetectorValueType& other) const;
+  bool operator< (const LeakDetectorValueType& other) const;
+
+ private:
+  Type type_;
+
+  uint32_t size_;
+  const CallStack* call_stack_;
+};
+
+}  // namespace leak_detector
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_VALUE_TYPE_