Change single-interface mojo bindings to use SequencedTaskRunner.

mojo/public/cpp/system/watcher.cc

Index: mojo/public/cpp/system/watcher.cc
diff --git a/mojo/public/cpp/system/watcher.cc b/mojo/public/cpp/system/watcher.cc
index 55dcf4023e2b719ea7e9fe28451c5280f05e9654..712d4d1413ea2266e76b5b27bfb0e7abf6bb33f5 100644
--- a/mojo/public/cpp/system/watcher.cc
+++ b/mojo/public/cpp/system/watcher.cc
@@ -7,19 +7,21 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/heap_profiler.h"
 #include "mojo/public/c/system/functions.h"
 
 namespace mojo {
 
 Watcher::Watcher(const tracked_objects::Location& from_here,
-                 scoped_refptr<base::SingleThreadTaskRunner> runner)
+                 scoped_refptr<base::SequencedTaskRunner> runner)
     : task_runner_(std::move(runner)),
-      is_default_task_runner_(task_runner_ ==
-                              base::ThreadTaskRunnerHandle::Get()),
+      is_default_task_runner_(base::ThreadTaskRunnerHandle::IsSet() &&
+                              task_runner_ ==
+                                  base::ThreadTaskRunnerHandle::Get()),
       heap_profiler_tag_(from_here.file_name()),
       weak_factory_(this) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   weak_self_ = weak_factory_.GetWeakPtr();
 }
 
@@ -29,14 +31,14 @@ Watcher::~Watcher() {
 }
 
 bool Watcher::IsWatching() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(sequence_checker_.CalledOnValidSequence());
   return handle_.is_valid();
 }
 
 MojoResult Watcher::Start(Handle handle,
                           MojoHandleSignals signals,
                           const ReadyCallback& callback) {
-  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(sequence_checker_.CalledOnValidSequence());
   DCHECK(!IsWatching());
   DCHECK(!callback.is_null());
 
@@ -57,7 +59,7 @@ MojoResult Watcher::Start(Handle handle,
 }
 
 void Watcher::Cancel() {
-  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(sequence_checker_.CalledOnValidSequence());
 
   // The watch may have already been cancelled if the handle was closed.
   if (!handle_.is_valid())
@@ -73,7 +75,7 @@ void Watcher::Cancel() {
 }
 
 void Watcher::OnHandleReady(MojoResult result) {
-  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(sequence_checker_.CalledOnValidSequence());
 
   ReadyCallback callback = callback_;
   if (result == MOJO_RESULT_CANCELLED) {