Add builders for tracing event's structural arguments

base/debug/trace_event_argument.h

Index: base/debug/trace_event_argument.h
diff --git a/base/debug/trace_event_argument.h b/base/debug/trace_event_argument.h
new file mode 100644
index 0000000000000000000000000000000000000000..6307ae47bf7152f445640d7466b02fc638d8b594
--- /dev/null
+++ b/base/debug/trace_event_argument.h
@@ -0,0 +1,174 @@
+// Copyright 2014 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_DEBUG_TRACE_EVENT_ARGUMENT_H_
+#define BASE_DEBUG_TRACE_EVENT_ARGUMENT_H_
+
+#include <string>
+#include <vector>
+
+#include "base/debug/trace_event.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace base {
+
+class DictionaryValue;
+class ListValue;
+class StringValue;
+class Value;
+
+template <class T>
+class TracedArray;
+
+class BASE_EXPORT TracedValueBase {
+ protected:
+  TracedValueBase();
+  ~TracedValueBase();
+
+  void SetInteger(const char* name, int value);
+  void SetDouble(const char* name, double);
+  void SetBoolean(const char* name, bool value);
+  void SetString(const char* name, const std::string& value);
+  void BeginDictionaryNamed(const char* name);
+  void BeginArrayNamed(const char* name);
+  void EndCurrentDictionary();
+
+  void PushInteger(int);
+  void PushDouble(double);
+  void PushBoolean(bool);
+  void PushString(const std::string&);
+  void PushArray();
+  void PushDictionary();
+  void EndCurrentArray();

[dsinclair, 2014/07/10 13:32:14]

nit: Move this up with EndCurrentDictionary() above.

[yurys, 2014/07/10 15:06:29]

Done.

+
+  DictionaryValue* GetCurrentDictionary() const;
+  ListValue* GetCurrentArray() const;
+
+  std::vector<Value*> m_stack;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TracedValueBase);
+};
+
+template <class OwnerType>
+class TracedDictionary : public TracedValueBase {
+ public:
+  OwnerType& EndDictionary() {
+    DCHECK(m_stack.size() == nestingLevel);
+    EndCurrentDictionary();
+    return *reinterpret_cast<OwnerType*>(this);
+  }
+
+  TracedDictionary<TracedDictionary<OwnerType> >& BeginDictionary(
+      const char* name) {
+    BeginDictionaryNamed(name);
+    return *reinterpret_cast<TracedDictionary<TracedDictionary<OwnerType> >*>(
+               this);
+  }
+  TracedArray<TracedDictionary<OwnerType> >& BeginArray(const char* name) {
+    BeginArrayNamed(name);
+    return *reinterpret_cast<TracedArray<TracedDictionary<OwnerType> >*>(this);
+  }
+  TracedDictionary<OwnerType>& SetInteger(const char* name, int value) {
+    TracedValueBase::SetInteger(name, value);
+    return *this;
+  }
+  TracedDictionary<OwnerType>& SetDouble(const char* name, double value) {
+    TracedValueBase::SetDouble(name, value);
+    return *this;
+  }
+  TracedDictionary<OwnerType>& SetBoolean(const char* name, bool value) {
+    TracedValueBase::SetBoolean(name, value);
+    return *this;
+  }
+  TracedDictionary<OwnerType>& SetString(const char* name,
+                                         const std::string& value) {
+    TracedValueBase::SetString(name, value);
+    return *this;
+  }
+
+  static const size_t nestingLevel = OwnerType::nestingLevel + 1;
+
+ private:
+  TracedDictionary();
+  ~TracedDictionary();
+  DISALLOW_COPY_AND_ASSIGN(TracedDictionary);
+};
+
+template <class OwnerType>
+class TracedArray : public TracedValueBase {
+ public:
+  TracedDictionary<TracedArray<OwnerType> >& BeginDictionary() {
+    PushDictionary();
+    return *reinterpret_cast<TracedDictionary<TracedArray<OwnerType> >*>(this);
+  }
+  TracedArray<TracedArray<OwnerType> >& BeginArray() {
+    PushArray();
+    return *reinterpret_cast<TracedArray<TracedArray<OwnerType> >*>(this);
+  }
+  OwnerType& EndArray() {
+    DCHECK(m_stack.size() == nestingLevel);
+    EndCurrentArray();
+    return *reinterpret_cast<OwnerType*>(this);
+  }
+
+  TracedArray<OwnerType>& PushInteger(int value) {
+    TracedValueBase::PushInteger(value);
+    return *this;
+  }
+  TracedArray<OwnerType>& PushDouble(double value) {
+    TracedValueBase::PushDouble(value);
+    return *this;
+  }
+  TracedArray<OwnerType>& PushBoolean(bool value) {
+    TracedValueBase::PushBoolean(value);
+    return *this;
+  }
+  TracedArray<OwnerType>& PushString(const std::string& value) {
+    TracedValueBase::PushString(value);
+    return *this;
+  }
+
+  static const size_t nestingLevel = OwnerType::nestingLevel + 1;
+
+ private:
+  TracedArray();
+  ~TracedArray();
+  DISALLOW_COPY_AND_ASSIGN(TracedArray);
+};
+
+class BASE_EXPORT TracedValue : public TracedValueBase {
+ public:
+  TracedValue();
+  ~TracedValue();
+
+  TracedDictionary<TracedValue>& BeginDictionary(const char* name);
+  TracedArray<TracedValue>& BeginArray(const char* name);
+  TracedValue& SetInteger(const char* name, int value) {
+    TracedValueBase::SetInteger(name, value);
+    return *this;
+  }
+  TracedValue& SetDouble(const char* name, double value) {
+    TracedValueBase::SetDouble(name, value);
+    return *this;
+  }
+  TracedValue& SetBoolean(const char* name, bool value) {
+    TracedValueBase::SetBoolean(name, value);
+    return *this;
+  }
+  TracedValue& SetString(const char* name, const std::string& value) {
+    TracedValueBase::SetString(name, value);
+    return *this;
+  }
+  scoped_refptr<base::debug::ConvertableToTraceFormat> finish();
+
+  static const size_t nestingLevel = 1;

[caseq, 2014/07/10 12:42:44]

nit: kNestingLevel?
Also, since it's never used as memory size or index, I guess int would be more
appropriate.

[yurys, 2014/07/10 12:50:50]

std::vector::size will return size_t and we compare it to nestingLevel, so the
type is size_t to avoid static_cast<size_t>.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TracedValue);
+};
+
+}  // namespace base
+
+#endif  // BASE_DEBUG_TRACE_EVENT_ARGUMENT_H_