cppgc: Fix GCInvoker task handle

The handle was always created empty which resulted in a DCHECK crash
in debug builds and in never-cancelled tasks in release builds.

Bug: chromium:1056170
Change-Id: I798ce65c37738bbe9c60b44b692ff04536f6d830
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2388101Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69653}

src/heap/cppgc/gc-invoker.cc

@@ -38,7 +38,9 @@ class GCInvoker::GCInvokerImpl final : public GarbageCollector {
     }
 
     explicit GCTask(GarbageCollector* collector)
-        : collector_(collector), saved_epoch_(collector->epoch()) {}
+        : collector_(collector),
+          handle_(Handle::NonEmptyTag{}),
+          saved_epoch_(collector->epoch()) {}
 
    private:
     void Run() final {

test/unittests/heap/cppgc/gc-invoker-unittest.cc

@@ -6,6 +6,7 @@
 
 #include "include/cppgc/platform.h"
 #include "src/heap/cppgc/heap.h"
+#include "test/unittests/heap/cppgc/test-platform.h"
 #include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -83,7 +84,7 @@ TEST(GCInvokerTest, ConservativeGCIsInvokedSynchronouslyWhenSupported) {
   invoker.CollectGarbage(GarbageCollector::Config::ConservativeAtomicConfig());
 }
 
-TEST(GCInvokerTest, ConservativeGCIsInvokedAsPreciseGCViaPlatform) {
+TEST(GCInvokerTest, ConservativeGCIsScheduledAsPreciseGCViaPlatform) {
   std::shared_ptr<cppgc::TaskRunner> runner =
       std::shared_ptr<cppgc::TaskRunner>(new MockTaskRunner());
   MockPlatform platform(runner);
@@ -96,6 +97,17 @@ TEST(GCInvokerTest, ConservativeGCIsInvokedAsPreciseGCViaPlatform) {
   invoker.CollectGarbage(GarbageCollector::Config::ConservativeAtomicConfig());
 }
 
+TEST(GCInvokerTest, ConservativeGCIsInvokedAsPreciseGCViaPlatform) {
+  testing::TestPlatform platform;
+  MockGarbageCollector gc;
+  GCInvoker invoker(&gc, &platform,
+                    cppgc::Heap::StackSupport::kNoConservativeStackScan);
+  EXPECT_CALL(gc, epoch).WillRepeatedly(::testing::Return(0));
+  EXPECT_CALL(gc, CollectGarbage);
+  invoker.CollectGarbage(GarbageCollector::Config::ConservativeAtomicConfig());
+  platform.WaitAllForegroundTasks();
+}
+
 TEST(GCInvokerTest, IncrementalGCIsStarted) {
   // Since StartIncrementalGarbageCollection doesn't scan the stack, support for
   // conservative stack scanning should not matter.

test/unittests/heap/cppgc/test-platform.h

@@ -19,13 +19,17 @@ namespace testing {
 class TestTaskRunner : public v8::TaskRunner {
  public:
   void PostTask(std::unique_ptr<v8::Task> task) override;
-  void PostNonNestableTask(std::unique_ptr<v8::Task> task) override;
   void PostDelayedTask(std::unique_ptr<v8::Task> task, double) override;
+
+  bool NonNestableTasksEnabled() const override { return true; }
+  void PostNonNestableTask(std::unique_ptr<v8::Task> task) override;
+
+  bool NonNestableDelayedTasksEnabled() const override { return true; }
   void PostNonNestableDelayedTask(std::unique_ptr<v8::Task> task,
                                   double) override;
 
-  void PostIdleTask(std::unique_ptr<v8::IdleTask> task) override;
   bool IdleTasksEnabled() override { return true; }
+  void PostIdleTask(std::unique_ptr<v8::IdleTask> task) override;
 
   bool RunSingleTask();
   bool RunSingleIdleTask(double duration_in_seconds);