Fix data races on |SharedMemoryDataConsumerHandle::Context::notification_task_runner_|

content/child/shared_memory_data_consumer_handle.cc

Index: content/child/shared_memory_data_consumer_handle.cc
diff --git a/content/child/shared_memory_data_consumer_handle.cc b/content/child/shared_memory_data_consumer_handle.cc
index f11435ada87c22572379c59ce9b80f2e50c85b44..7206ca6ee7b0103520008c129a5e4da1a0fc378b 100644
--- a/content/child/shared_memory_data_consumer_handle.cc
+++ b/content/child/shared_memory_data_consumer_handle.cc
@@ -104,7 +104,11 @@ class SharedMemoryDataConsumerHandle::Context final
     client_ = nullptr;
   }
   void PostNotify() {
-    auto runner = notification_task_runner_;
+    scoped_refptr<base::SingleThreadTaskRunner> runner;
+    {
+      base::AutoLock lock(lock_);
+      runner = notification_task_runner_;
+    }
     if (!runner)
       return;
     // We don't re-post the task when the runner changes while waiting for
@@ -160,7 +164,11 @@ class SharedMemoryDataConsumerHandle::Context final
   void NotifyInternal(bool repost) {
     // Note that this function is not protected by |lock_|.
 
-    auto runner = notification_task_runner_;
+    scoped_refptr<base::SingleThreadTaskRunner> runner;
+    {
+      base::AutoLock lock(lock_);
+      runner = notification_task_runner_;
+    }
     if (!runner)
       return;