Media Capabilities: stub implementation of mediaCapabilities.query().

third_party/WebKit/Source/modules/mediacapabilities/NavigatorMediaCapabilities.cpp

+// Copyright 2017 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 "modules/mediacapabilities/NavigatorMediaCapabilities.h"
+
+#include "modules/mediacapabilities/MediaCapabilities.h"
+#include "platform/Supplementable.h"
+
+namespace blink {
+
+MediaCapabilities* NavigatorMediaCapabilities::mediaCapabilities(
+    Navigator& navigator) {
+  NavigatorMediaCapabilities& self =
+      NavigatorMediaCapabilities::from(navigator);
+  if (!self.m_capabilities)
+    self.m_capabilities = new MediaCapabilities();
+  return self.m_capabilities.get();
+}
+
+DEFINE_TRACE(NavigatorMediaCapabilities) {
+  visitor->trace(m_capabilities);
+  Supplement<Navigator>::trace(visitor);
+}
+
+NavigatorMediaCapabilities::NavigatorMediaCapabilities(Navigator& navigator)
+    : Supplement<Navigator>(navigator) {}
+
+NavigatorMediaCapabilities& NavigatorMediaCapabilities::from(
+    Navigator& navigator) {
+  NavigatorMediaCapabilities* supplement =
+      static_cast<NavigatorMediaCapabilities*>(

[chcunningham, 2017/02/13 19:31:07]

I notice this comment:

// Supplementable and Supplement instances are meant to be thread local. They
// should only be accessed from within the thread that created them.

Is that restriction still met if someone accesses this API from a worker thread?

[mlamouri (slow - plz ping), 2017/02/13 22:58:25]

It wouldn't because workers would have a different instance. Workers do not use
vanilla Navigator.

+          Supplement<Navigator>::from(navigator, supplementName()));
+  if (!supplement) {
+    supplement = new NavigatorMediaCapabilities(navigator);
+    provideTo(navigator, supplementName(), supplement);
+  }
+  return *supplement;
+}
+
+const char* NavigatorMediaCapabilities::supplementName() {
+  return "NavigatorMediaCapabilities";
+}
+
+}  // namespace blink