[OfflinePages] Clear busy flag in StopPrerendering() in Request Coordinator.

components/offline_pages/background/request_coordinator_unittest.cc

Index: components/offline_pages/background/request_coordinator_unittest.cc
diff --git a/components/offline_pages/background/request_coordinator_unittest.cc b/components/offline_pages/background/request_coordinator_unittest.cc
index d63409ed2d579cfba0a43c51ee3669b9ecf39f4f..2aa6565e846afcc1eba564126e96cb27ec1411ce 100644
--- a/components/offline_pages/background/request_coordinator_unittest.cc
+++ b/components/offline_pages/background/request_coordinator_unittest.cc
@@ -607,12 +607,17 @@ TEST_F(RequestCoordinatorTest, StartProcessingThenStopProcessingLater) {
   // Let all the async parts of the start processing pipeline run to completion.
   PumpLoop();
 
+  // Coordinator should now be busy.
+  EXPECT_TRUE(is_busy());
+
   // Now we cancel it while the prerenderer is busy.
   coordinator()->StopProcessing();
 
   // Let the async callbacks in the cancel run.
   PumpLoop();
 
+  EXPECT_FALSE(is_busy());
+
   // OfflinerDoneCallback will not end up getting called with status SAVED,
   // since we cancelled the event before the LoadAndSave completed.
   EXPECT_EQ(Offliner::RequestStatus::REQUEST_COORDINATOR_CANCELED,