base: Add three helper functions to Values API.

base/values.cc

Index: base/values.cc
diff --git a/base/values.cc b/base/values.cc
index 7a364bd8ff0f14402dac1ff80b5f6b72b656a9d2..12271df03b6cbe2c7d4ecdc5a7b7db071eb55224 100644
--- a/base/values.cc
+++ b/base/values.cc
@@ -57,6 +57,14 @@ Value* CopyWithoutEmptyChildren(Value* node) {
   }
 }
 
+class Null : public Value {
+ public:
+  Null() : Value(TYPE_NULL) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Null);
+};
+
 }  // namespace
 
 namespace base {
@@ -67,11 +75,6 @@ Value::~Value() {
 }
 
 // static
-Value* Value::CreateNullValue() {
-  return new Value(TYPE_NULL);
-}
-
-// static
 FundamentalValue* Value::CreateBooleanValue(bool in_value) {
   return new FundamentalValue(in_value);
 }
@@ -128,7 +131,7 @@ Value* Value::DeepCopy() const {
   // This method should only be getting called for null Values--all subclasses
   // need to provide their own implementation;.
   DCHECK(IsType(TYPE_NULL));
-  return CreateNullValue();
+  return NullValue();
 }
 
 bool Value::Equals(const Value* other) const {
@@ -148,7 +151,21 @@ bool Value::Equals(const Value* a, const Value* b) {
 Value::Value(Type type) : type_(type) {
 }
 
-///////////////////// FundamentalValue ////////////////////
+// Helper functions ------------------------------------------------------------
+
+Value* NullValue() {
+  return new Null();
+}
+
+FundamentalValue* TrueValue() {
+  return new FundamentalValue(true);
+}
+
+FundamentalValue* FalseValue() {
+  return new FundamentalValue(false);
+}
+
+// FundamentalValue ------------------------------------------------------------
 
 FundamentalValue::FundamentalValue(bool in_value)
     : Value(TYPE_BOOLEAN), boolean_value_(in_value) {
@@ -225,7 +242,7 @@ bool FundamentalValue::Equals(const Value* other) const {
   }
 }
 
-///////////////////// StringValue ////////////////////
+// StringValue -----------------------------------------------------------------
 
 StringValue::StringValue(const std::string& in_value)
     : Value(TYPE_STRING),
@@ -264,7 +281,7 @@ bool StringValue::Equals(const Value* other) const {
   return GetAsString(&lhs) && other->GetAsString(&rhs) && lhs == rhs;
 }
 
-///////////////////// BinaryValue ////////////////////
+// BinaryValue -----------------------------------------------------------------
 
 BinaryValue::~BinaryValue() {
   DCHECK(buffer_);
@@ -311,7 +328,7 @@ BinaryValue::BinaryValue(char* buffer, size_t size)
   DCHECK(buffer_);
 }
 
-///////////////////// DictionaryValue ////////////////////
+// DictionaryValue -------------------------------------------------------------
 
 DictionaryValue::DictionaryValue()
     : Value(TYPE_DICTIONARY) {
@@ -687,7 +704,7 @@ bool DictionaryValue::Equals(const Value* other) const {
   return true;
 }
 
-///////////////////// ListValue ////////////////////
+// ListValue -------------------------------------------------------------------
 
 ListValue::ListValue() : Value(TYPE_LIST) {
 }
@@ -709,7 +726,7 @@ bool ListValue::Set(size_t index, Value* in_value) {
   if (index >= list_.size()) {
     // Pad out any intermediate indexes with null settings
     while (index > list_.size())
-      Append(CreateNullValue());
+      Append(NullValue());
     Append(in_value);
   } else {
     DCHECK(list_[index] != in_value);
@@ -899,7 +916,4 @@ bool ListValue::Equals(const Value* other) const {
   return true;
 }
 
-ValueSerializer::~ValueSerializer() {
-}
-
 }  // namespace base