Plumbing from WebPresentationClient to the Presentation Mojo service for

content/renderer/presentation/presentation_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/presentation/presentation_dispatcher.h"
+
+#include "content/common/presentation/presentation_service.mojom.h"
+#include "content/public/common/service_registry.h"
+#include "content/public/renderer/render_frame.h"
+#include "third_party/WebKit/public/platform/WebPresentationController.h"
+
+namespace content {
+
+PresentationDispatcher::PresentationDispatcher(RenderFrame* render_frame)
+    : RenderFrameObserver(render_frame),
+      controller_(nullptr) {
+}
+
+PresentationDispatcher::~PresentationDispatcher() {
+  if (controller_) {
+    updateAvailableChangeWatched(false);
+    controller_->onClientDestroyed();
+  }
+}
+
+void PresentationDispatcher::setController(
+    blink::WebPresentationController* controller) {
+  // There shouldn't be any swapping from one non-null controller to another.
+  CHECK(controller != controller_ && (!controller || !controller_));

[Avi (use Gerrit), 2015/01/28 19:04:05]

Why CHECK? We usually do DCHECK for programming errors.

[whywhat, 2015/01/28 20:26:04]

Done.

+  controller_ = controller;
+
+  // Notify the service that the controller has changed so it could either
+  // stop or start sending the availability events.
+  updateAvailableChangeWatched(
+      controller && controller->isAvailableChangeWatched());
+}
+
+void PresentationDispatcher::updateAvailableChangeWatched(bool watched) {
+  ConnectToPresentationServiceIfNeeded();
+  if (watched) {
+    presentation_service_->GetScreenAvailability(
+        mojo::String(),
+        base::Bind(&PresentationDispatcher::OnScreenAvailabilityChanged,
+                 base::Unretained(this)));
+  } else {
+    presentation_service_->OnScreenAvailabilityListenerRemoved();
+  }
+}
+
+void PresentationDispatcher::OnScreenAvailabilityChanged(bool available) {
+  if (!controller_)
+    return;
+
+  // Reset the callback to get the next event.
+  updateAvailableChangeWatched(controller_->isAvailableChangeWatched());
+
+  controller_->didChangeAvailability(available);
+}
+
+void PresentationDispatcher::ConnectToPresentationServiceIfNeeded() {
+  if (presentation_service_.get())
+    return;
+
+  render_frame()->GetServiceRegistry()->ConnectToRemoteService(
+      &presentation_service_);
+}
+
+}  // namespace content