Fix ImageResourceTest.CancelWithImageAndFinishObserver to pass

ImageResourceTest.CancelWithImageAndFinishObserver had two problems:

- ResourceFinishObserver::NotifyFinished was not getting called because blink::test::RunPendingTasks() doesn't run tasks in FakeTaskRunners.
- Test failure was treated as passing because EXPECT_CALL was checked in the MockImageObserver destructor which runs in a GC after the test.

This CL replaces RunPendingTasks() call with FakeTaskRunner::RunUntilIdle() to fix the first issue.
And adds an explicit GC in TearDown so EXPECT_CALL gets checked inside the test.


Bug: 1138819
Change-Id: Ic0d0c089cab5e728d65f3e947e0b9b36a066395f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2507314Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823922}

third_party/blink/renderer/core/loader/resource/image_resource_test.cc

@@ -118,7 +118,14 @@ constexpr size_t kJpegImageSubrangeWithDimensionsLength =
 constexpr size_t kJpegImageSubrangeWithoutDimensionsLength = 3;
 
 class ImageResourceTest : public testing::Test,
-                          private ScopedMockOverlayScrollbars {};
+                          private ScopedMockOverlayScrollbars {
+  void TearDown() override {
+    // Trigger a GC so MockFinishObserver gets destroyed and EXPECT_CALL gets
+    // checked before the test ends.
+    ThreadState::Current()->CollectAllGarbageForTesting(
+        BlinkGC::kNoHeapPointersOnStack);
+  }
+};
 
 // Ensure that the image decoder can determine the dimensions of kJpegImage from
 // just the first kJpegImageSubrangeWithDimensionsLength bytes. If this test
@@ -398,6 +405,8 @@ TEST_F(ImageResourceTest, CancelWithImageAndFinishObserver) {
   ScopedMockedURLLoad scoped_mocked_url_load(test_url, GetTestFilePath());
 
   ResourceFetcher* fetcher = CreateFetcher();
+  scheduler::FakeTaskRunner* task_runner =
+      static_cast<scheduler::FakeTaskRunner*>(fetcher->GetTaskRunner().get());
 
   // Emulate starting a real load.
   ImageResource* image_resource = ImageResource::CreateForTest(test_url);
@@ -427,7 +436,7 @@ TEST_F(ImageResourceTest, CancelWithImageAndFinishObserver) {
 
   // ResourceFinishObserver is notified asynchronously.
   EXPECT_CALL(*finish_observer, NotifyFinished());
-  blink::test::RunPendingTasks();
+  task_runner->RunUntilIdle();
 }
 
 TEST_F(ImageResourceTest, DecodedDataRemainsWhileHasClients) {