api: Make Context a Data object

Context objects are allocated on the heap and thus should be Data
objects. This allows handling them through tracing in the GC through
the API.

Bug: chromium:1013149
Change-Id: Id3a7bfd57fab19a5669062ccf61c2f8588faf0bb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2627307Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72120}

include/v8.h

@@ -1343,6 +1343,11 @@ class V8_EXPORT Data {
    */
   bool IsFunctionTemplate() const;
 
+  /**
+   * Returns true if this data is a |v8::Context|.
+   */
+  bool IsContext() const;
+
  private:
   Data();
 };
@@ -10439,7 +10444,7 @@ class V8_EXPORT ExtensionConfiguration {
  * A sandboxed execution context with its own set of built-in objects
  * and functions.
  */
-class V8_EXPORT Context {
+class V8_EXPORT Context : public Data {
  public:
   /**
    * Returns the global proxy object.
@@ -10716,18 +10721,21 @@ class V8_EXPORT Context {
     const BackupIncumbentScope* prev_ = nullptr;
   };
 
+  V8_INLINE static Context* Cast(Data* data);
+
  private:
   friend class Value;
   friend class Script;
   friend class Object;
   friend class Function;
 
+  static void CheckCast(Data* obj);
+
   internal::Address* GetDataFromSnapshotOnce(size_t index);
   Local<Value> SlowGetEmbedderData(int index);
   void* SlowGetAlignedPointerFromEmbedderData(int index);
 };
 
-
 /**
  * Multiple threads in V8 are allowed, but only one thread at a time is allowed
  * to use any given V8 isolate, see the comments in the Isolate class. The
@@ -11896,6 +11904,13 @@ BigInt* BigInt::Cast(v8::Data* data) {
   return static_cast<BigInt*>(data);
 }
 
+Context* Context::Cast(v8::Data* data) {
+#ifdef V8_ENABLE_CHECKS
+  CheckCast(data);
+#endif
+  return static_cast<Context*>(data);
+}
+
 Date* Date::Cast(v8::Value* value) {
 #ifdef V8_ENABLE_CHECKS
   CheckCast(value);

src/api/api.cc

@@ -1183,6 +1183,8 @@ bool Data::IsFunctionTemplate() const {
   return Utils::OpenHandle(this)->IsFunctionTemplateInfo();
 }
 
+bool Data::IsContext() const { return Utils::OpenHandle(this)->IsContext(); }
+
 void Context::Enter() {
   i::Handle<i::Context> env = Utils::OpenHandle(this);
   i::Isolate* isolate = env->GetIsolate();
@@ -3881,6 +3883,12 @@ void v8::BigInt::CheckCast(v8::Data* that) {
                   "Value is not a BigInt");
 }
 
+void v8::Context::CheckCast(v8::Data* that) {
+  i::Handle<i::Object> obj = Utils::OpenHandle(that);
+  Utils::ApiCheck(obj->IsContext(), "v8::Context::Cast",
+                  "Value is not a Context");
+}
+
 void v8::Array::CheckCast(Value* that) {
   i::Handle<i::Object> obj = Utils::OpenHandle(that);
   Utils::ApiCheck(obj->IsJSArray(), "v8::Array::Cast", "Value is not an Array");