Add a few extra tests for throttling corner cases

components/scheduler/renderer/throttling_helper_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/scheduler/renderer/throttling_helper.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 410 matching lines @@
   throttling_helper_->IncreaseThrottleRefCount(timer_queue_.get());
   EXPECT_FALSE(timer_queue_->IsQueueEnabled());
 
   mock_task_runner_->RunUntilIdle();  // Wait until the pump.
   EXPECT_TRUE(timer_queue_->IsQueueEnabled());
 
   throttling_helper_->SetQueueEnabled(timer_queue_.get(), false);
   EXPECT_FALSE(timer_queue_->IsQueueEnabled());
 }
 
+TEST_F(ThrottlingHelperTest, DoubleIncrementDoubleDecrement) {
+  timer_queue_->PostTask(FROM_HERE, base::Bind(&NopTask));
+
+  EXPECT_TRUE(timer_queue_->IsQueueEnabled());
+  throttling_helper_->IncreaseThrottleRefCount(timer_queue_.get());
+  throttling_helper_->IncreaseThrottleRefCount(timer_queue_.get());
+  EXPECT_FALSE(timer_queue_->IsQueueEnabled());
+  throttling_helper_->DecreaseThrottleRefCount(timer_queue_.get());
+  throttling_helper_->DecreaseThrottleRefCount(timer_queue_.get());
+  EXPECT_TRUE(timer_queue_->IsQueueEnabled());
+}
+
 }  // namespace scheduler