heap/cppgc: Add helpers for Persistent and friends

Bug: chromium:1056170
Change-Id: I3754025e8d935887cdbfa6d2c517c715dabc09d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532080
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827242}

third_party/blink/renderer/platform/heap/v8_wrapper/persistent.h

@@ -5,7 +5,11 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_V8_WRAPPER_PERSISTENT_H_
 #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_V8_WRAPPER_PERSISTENT_H_
 
+#include "base/bind.h"
+#include "third_party/blink/renderer/platform/wtf/type_traits.h"
+#include "v8/include/cppgc/cross-thread-persistent.h"
 #include "v8/include/cppgc/persistent.h"
+#include "v8/include/cppgc/source-location.h"
 
 namespace blink {
 
@@ -15,6 +19,68 @@ using Persistent = cppgc::Persistent<T>;
 template <typename T>
 using WeakPersistent = cppgc::WeakPersistent<T>;
 
+template <typename T>
+using CrossThreadPersistent = cppgc::subtle::CrossThreadPersistent<T>;
+
+template <typename T>
+using CrossThreadWeakPersistent = cppgc::subtle::WeakCrossThreadPersistent<T>;
+
+template <typename T>
+Persistent<T> WrapPersistent(
+    T* value,
+    const cppgc::SourceLocation& loc = cppgc::SourceLocation::Current()) {
+  return Persistent<T>(value, loc);
+}
+
+template <typename T>
+WeakPersistent<T> WrapWeakPersistent(
+    T* value,
+    const cppgc::SourceLocation& loc = cppgc::SourceLocation::Current()) {
+  return WeakPersistent<T>(value, loc);
+}
+
+template <typename T>
+CrossThreadPersistent<T> WrapCrossthreadPersistent(
+    T* value,
+    const cppgc::SourceLocation& loc = cppgc::SourceLocation::Current()) {
+  return CrossThreadPersistent<T>(value, loc);
+}
+
+template <typename T>
+CrossThreadWeakPersistent<T> WrapCrossThreadWeakPersistent(
+    T* value,
+    const cppgc::SourceLocation& loc = cppgc::SourceLocation::Current()) {
+  return CrossThreadWeakPersistent<T>(value, loc);
+}
+
+template <typename T,
+          typename = std::enable_if_t<WTF::IsGarbageCollectedType<T>::value>>
+Persistent<T> WrapPersistentIfNeeded(T* value) {
+  return Persistent<T>(value);
+}
+
+template <typename T>
+T& WrapPersistentIfNeeded(T& value) {
+  return value;
+}
+
 }  // namespace blink
 
+namespace base {
+
+template <typename T>
+struct IsWeakReceiver<blink::WeakPersistent<T>> : std::true_type {};
+
+template <typename T>
+struct IsWeakReceiver<blink::CrossThreadWeakPersistent<T>> : std::true_type {};
+
+template <typename T>
+struct BindUnwrapTraits<blink::CrossThreadWeakPersistent<T>> {
+  static blink::CrossThreadPersistent<T> Unwrap(
+      const blink::CrossThreadWeakPersistent<T>& wrapped) {
+    return blink::CrossThreadPersistent<T>(wrapped);
+  }
+};
+}  // namespace base
+
 #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_V8_WRAPPER_PERSISTENT_H_