[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/watcher.cc

+// Copyright 2016 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 "mojo/edk/system/watcher.h"
+
+#include "mojo/edk/system/request_context.h"
+
+namespace mojo {
+namespace edk {
+
+Watcher::Watcher(MojoHandleSignals signals, const WatchCallback& callback)
+    : signals_(signals), callback_(callback) {
+}
+
+void Watcher::MaybeInvokeCallback(MojoResult result,
+                                  MojoHandleSignalsState state) {
+  base::AutoLock lock(lock_);
+  if (is_cancelled_)
+    return;
+
+  callback_.Run(result, state);
+}
+
+void Watcher::NotifyForStateChange(MojoHandleSignalsState signals_state) {

[Anand Mistry (off Chromium), 2016/03/01 07:30:40]

Can't you use mojo::HandleSignalsState here as well, then use .can_satisfy() in
the condition below? Really, any place you can use it, you should. It's only
data that comes from the user via the public API that needs to be
MojoHandleSignalsState.

[Ken Rockot(use gerrit already), 2016/03/01 08:17:44]

Done here and everywhere else it's possible

+  RequestContext* request_context = RequestContext::current();
+  if (signals_state.satisfied_signals & signals_) {
+    request_context->AddWatchFinalizer(
+        make_scoped_refptr(this), MOJO_RESULT_OK, signals_state);
+  } else if (!(signals_state.satisfiable_signals & signals_)) {
+    request_context->AddWatchFinalizer(make_scoped_refptr(this),
+                                       MOJO_RESULT_FAILED_PRECONDITION,
+                                       signals_state);
+  }
+}
+
+void Watcher::NotifyClosed() {
+  static const MojoHandleSignalsState closed_state = {0, 0};
+  RequestContext::current()->AddWatchFinalizer(
+      make_scoped_refptr(this), MOJO_RESULT_CANCELLED, closed_state);
+}
+
+void Watcher::Cancel() {
+  base::AutoLock lock(lock_);
+  is_cancelled_ = true;
+}
+
+Watcher::~Watcher() {}
+
+}  // namespace edk
+}  // namespace mojo