Add Cast() to Boolean

We should be able to cast a Value to Boolean when IsBoolean() is true.

Review URL: https://codereview.chromium.org/990943003

Cr-Commit-Position: refs/heads/master@{#27124}

include/v8.h

@@ -2007,7 +2007,10 @@ class V8_EXPORT Primitive : public Value { };
 class V8_EXPORT Boolean : public Primitive {
  public:
   bool Value() const;
+  V8_INLINE static Boolean* Cast(v8::Value* obj);
   V8_INLINE static Handle<Boolean> New(Isolate* isolate, bool value);
+ private:
+  static void CheckCast(v8::Value* obj);
 };
 
 
@@ -7314,6 +7317,14 @@ Local<Uint32> Value::ToUint32() const {
 Local<Int32> Value::ToInt32() const { return ToInt32(Isolate::GetCurrent()); }
 
 
+Boolean* Boolean::Cast(v8::Value* value) {
+#ifdef V8_ENABLE_CHECKS
+  CheckCast(value);
+#endif
+  return static_cast<Boolean*>(value);
+}
+
+
 Name* Name::Cast(v8::Value* value) {
 #ifdef V8_ENABLE_CHECKS
   CheckCast(value);

src/api.cc

@@ -2933,6 +2933,14 @@ void v8::Function::CheckCast(Value* that) {
 }
 
 
+void v8::Boolean::CheckCast(v8::Value* that) {
+  i::Handle<i::Object> obj = Utils::OpenHandle(that);
+  Utils::ApiCheck(obj->IsBoolean(),
+                  "v8::Boolean::Cast()",
+                  "Could not convert to boolean");
+}
+
+
 void v8::Name::CheckCast(v8::Value* that) {
   i::Handle<i::Object> obj = Utils::OpenHandle(that);
   Utils::ApiCheck(obj->IsName(),