Change single-interface mojo bindings to use SequencedTaskRunner.

mojo/public/cpp/system/watcher.h

Index: mojo/public/cpp/system/watcher.h
diff --git a/mojo/public/cpp/system/watcher.h b/mojo/public/cpp/system/watcher.h
index 236788b1c853139367df8b0a56b44859064219ca..7bcf15da8a240cba471128d777f9c55bb37f53df 100644
--- a/mojo/public/cpp/system/watcher.h
+++ b/mojo/public/cpp/system/watcher.h
@@ -9,9 +9,9 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "base/single_thread_task_runner.h"
-#include "base/threading/thread_checker.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/sequence_checker.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/sequenced_task_runner_handle.h"
 #include "mojo/public/c/system/types.h"
 #include "mojo/public/cpp/system/handle.h"
 #include "mojo/public/cpp/system/system_export.h"
@@ -37,8 +37,8 @@ class MOJO_CPP_SYSTEM_EXPORT Watcher {
   using ReadyCallback = base::Callback<void(MojoResult result)>;
 
   Watcher(const tracked_objects::Location& from_here,
-          scoped_refptr<base::SingleThreadTaskRunner> runner =
-              base::ThreadTaskRunnerHandle::Get());
+          scoped_refptr<base::SequencedTaskRunner> runner =
+                       base::SequencedTaskRunnerHandle::Get());
 
   // NOTE: This destructor automatically calls |Cancel()| if the Watcher is
   // still active.
@@ -89,11 +89,11 @@ class MOJO_CPP_SYSTEM_EXPORT Watcher {
                                 MojoHandleSignalsState signals_state,
                                 MojoWatchNotificationFlags flags);
 
-  base::ThreadChecker thread_checker_;
+  base::SequenceChecker sequence_checker_;
 
   // The TaskRunner of this Watcher's owning thread. This field is safe to
   // access from any thread.
-  const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  const scoped_refptr<base::SequencedTaskRunner> task_runner_;
   // Whether |task_runner_| is the same as base::ThreadTaskRunnerHandle::Get()
   // for the thread.
   const bool is_default_task_runner_;