media: Add MediaPermission interface and MediaPermissionDispatcher.

content/renderer/media/media_permission_dispatcher.cc

+// Copyright 2015 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 "content/renderer/media/media_permission_dispatcher.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "content/public/common/service_registry.h"
+#include "content/public/renderer/render_frame.h"
+#include "third_party/WebKit/public/web/WebUserGestureIndicator.h"
+#include "url/gurl.h"
+
+namespace content {
+
+MediaPermissionDispatcher::MediaPermissionDispatcher(RenderFrame* render_frame)
+    : RenderFrameObserver(render_frame), next_request_id_(0) {
+}
+
+MediaPermissionDispatcher::~MediaPermissionDispatcher() {

[xhwang, 2015/01/22 23:40:54]

Since |this| is a RenderFrameObserver, this is only called when the RenderFrame
is destroyed. In that case, the browser side will cancel the requests:
https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/pe...

+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  // Fire all pending callbacks with |false|.
+  for (auto& request : requests_)
+    request.second.Run(false);
+
+  requests_.clear();
+}
+
+void MediaPermissionDispatcher::HasPermission(
+    Type type,
+    const GURL& security_origin,
+    const PermissionStatusCB& permission_status_cb) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  CHECK_EQ(PROTECTED_MEDIA_IDENTIFIER, type);
+
+  if (!permission_service_.get()) {
+    render_frame()->GetServiceRegistry()->ConnectToRemoteService(
+        &permission_service_);
+  }
+
+  uint32_t request_id = next_request_id_++;
+  DCHECK(!requests_.count(request_id));
+  requests_[request_id] = permission_status_cb;
+
+  DVLOG(2) << __FUNCTION__ << ": request ID " << request_id;
+
+  permission_service_->HasPermission(
+      PERMISSION_NAME_PROTECTED_MEDIA_IDENTIFIER, security_origin.spec(),
+      base::Bind(&MediaPermissionDispatcher::OnPermissionStatus,
+                 base::Unretained(this), request_id));
+}
+
+void MediaPermissionDispatcher::RequestPermission(
+    Type type,
+    const GURL& security_origin,
+    const PermissionStatusCB& permission_status_cb) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  CHECK_EQ(PROTECTED_MEDIA_IDENTIFIER, type);
+
+  if (!permission_service_.get()) {
+    render_frame()->GetServiceRegistry()->ConnectToRemoteService(
+        &permission_service_);
+  }
+
+  uint32_t request_id = next_request_id_++;
+  DCHECK(!requests_.count(request_id));
+  requests_[request_id] = permission_status_cb;
+
+  DVLOG(2) << __FUNCTION__ << ": request ID " << request_id;
+
+  permission_service_->RequestPermission(
+      PERMISSION_NAME_PROTECTED_MEDIA_IDENTIFIER, security_origin.spec(),
+      blink::WebUserGestureIndicator::isProcessingUserGesture(),
+      base::Bind(&MediaPermissionDispatcher::OnPermissionStatus,
+                 base::Unretained(this), request_id));

[xhwang, 2015/01/22 23:40:54]

base::Unretained(this) is also used in other dispatchers:
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/n...

I *think* it's safe because this class is a RenderFrameObserver. When the render
frame is destroyed, the browser side will get notified and will never return the
status back.

+}
+
+void MediaPermissionDispatcher::OnPermissionStatus(uint32_t request_id,
+                                                   PermissionStatus status) {
+  DVLOG(2) << __FUNCTION__ << ": (" << request_id << ", " << status << ")";
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  RequestMap::iterator iter = requests_.find(request_id);
+  if (iter == requests_.end()) {
+    DVLOG(2) << "Request not found.";
+    return;
+  }
+
+  PermissionStatusCB permission_status_cb = iter->second;
+  requests_.erase(iter);
+
+  permission_status_cb.Run(status == PERMISSION_STATUS_GRANTED);
+}
+
+}  // namespace content