Add a few extra tests for throttling corner cases

components/scheduler/renderer/throttling_helper_unittest.cc

Index: components/scheduler/renderer/throttling_helper_unittest.cc
diff --git a/components/scheduler/renderer/throttling_helper_unittest.cc b/components/scheduler/renderer/throttling_helper_unittest.cc
index 360c13d25da264cbe39c57cef7a9cece72ba2324..117e9a2baa0489dc506b2c563b69207870db5c20 100644
--- a/components/scheduler/renderer/throttling_helper_unittest.cc
+++ b/components/scheduler/renderer/throttling_helper_unittest.cc
@@ -428,4 +428,16 @@ TEST_F(ThrottlingHelperTest, TaskQueueDisabledTillPump_ThenManuallyDisabled) {
   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