[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/request_context.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/request_context.h"
+
+#include "base/threading/thread_local.h"
+
+namespace mojo {
+namespace edk {
+
+namespace {
+
+base::ThreadLocalPointer<RequestContext> g_current_context;

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

Needs to be a LazyInstance, otherwise you're introducing a static initializer.

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

done

+
+}  // namespace
+
+RequestContext::RequestContext() {
+  // We allow nested RequestContexts to exist as long as they aren't actually
+  // used for anything.
+  if (!g_current_context.Get())
+    g_current_context.Set(this);
+}
+
+RequestContext::~RequestContext() {
+  // NOTE: Callbacks invoked by this destructor are allowed to initiate new
+  // EDK requests on this thread, so we need to reset the thread-local context
+  // pointer before calling them.
+  if (IsCurrent())
+    g_current_context.Set(nullptr);
+
+  for (const WatchFinalizer& watch : watch_finalizers_.container())
+    watch.watcher->MaybeInvokeCallback(watch.result, watch.state);
+}
+
+// static
+RequestContext* RequestContext::current() {
+  DCHECK(g_current_context.Get());
+  return g_current_context.Get();
+}
+
+void RequestContext::AddWatchFinalizer(
+    scoped_refptr<Watcher> watcher,
+    MojoResult result,
+    MojoHandleSignalsState state) {
+  DCHECK(IsCurrent());
+  watch_finalizers_->push_back(WatchFinalizer(watcher, result, state));
+}
+
+bool RequestContext::IsCurrent() const {
+  return g_current_context.Get() == this;
+}
+
+RequestContext::WatchFinalizer::WatchFinalizer(
+    scoped_refptr<Watcher> watcher,
+    MojoResult result,
+    MojoHandleSignalsState state)
+    : watcher(watcher), result(result), state(state) {
+}
+
+RequestContext::WatchFinalizer::~WatchFinalizer() {}
+
+}  // namespace edk
+}  // namespace mojo