Adds Mojo IDL.

third_party/WebKit/Source/core/mojo/MojoHandleWatcher.cpp

+// 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 "core/mojo/MojoHandleWatcher.h"
+
+#include "public/platform/WebTaskRunner.h"
+
+namespace blink {
+
+class MojoHandleWatcher::RunReadyCallbackTask : public WebTaskRunner::Task {
+ public:
+  RunReadyCallbackTask(MojoHandleWatcher* watcher, MojoResult result)
+      : m_watcher(watcher), m_result(result) {}
+  void run() final { m_watcher->runReadyCallback(m_result); }
+
+ private:
+  MojoHandleWatcher* m_watcher;
+  MojoResult m_result;
+};
+
+MojoHandleWatcher::MojoHandleWatcher(WebTaskRunner* taskRunner)
+    : m_taskRunner(taskRunner), m_handle(MOJO_HANDLE_INVALID) {}
+
+MojoHandleWatcher::~MojoHandleWatcher() {
+  DCHECK(m_taskRunner->runsTasksOnCurrentThread());
+
+  if (m_handle != MOJO_HANDLE_INVALID)
+    cancel();
+}
+
+MojoResult MojoHandleWatcher::start(MojoHandle handle,
+                                    MojoHandleSignals signals,
+                                    std::unique_ptr<ReadyCallback> callback) {
+  DCHECK(m_taskRunner->runsTasksOnCurrentThread());
+  DCHECK(handle != MOJO_HANDLE_INVALID);
+  DCHECK(callback);
+
+  MojoResult result =
+      MojoWatch(handle, signals, &MojoHandleWatcher::onHandleReady,
+                reinterpret_cast<uintptr_t>(this));
+
+  if (result == MOJO_RESULT_OK) {
+    m_handle = handle;
+    m_callback = std::move(callback);
+  }
+  return result;
+}
+
+void MojoHandleWatcher::cancel() {
+  DCHECK(m_taskRunner->runsTasksOnCurrentThread());
+  DCHECK(m_handle != MOJO_HANDLE_INVALID);
+
+  MojoCancelWatch(m_handle, reinterpret_cast<uintptr_t>(this));
+  m_handle = MOJO_HANDLE_INVALID;
+  m_callback.reset();
+}
+
+void MojoHandleWatcher::onHandleReady(uintptr_t context,
+                                      MojoResult result,
+                                      MojoHandleSignalsState,
+                                      MojoWatchNotificationFlags) {
+  MojoHandleWatcher* watcher = reinterpret_cast<MojoHandleWatcher*>(context);

[Ken Rockot(use gerrit already), 2016/10/18 15:47:10]

Please explicitly document here that |watcher| is guaranteed to remain alive
through the extent of onHandleReady.

[alokp, 2016/10/18 16:48:37]

Done.

+  if (watcher->m_taskRunner->runsTasksOnCurrentThread()) {
+    watcher->runReadyCallback(result);
+  } else {
+    watcher->m_taskRunner->postTask(BLINK_FROM_HERE,
+                                    new RunReadyCallbackTask(watcher, result));
+  }
+}
+
+void MojoHandleWatcher::runReadyCallback(MojoResult result) {
+  DCHECK(m_taskRunner->runsTasksOnCurrentThread());
+  (*m_callback)(result);
+}
+
+}  // namespace blink