Defer loading of audio/video tags while prerendering.

chrome/renderer/prerender/prerender_webmediaplayer.cc

+// Copyright (c) 2011 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 "chrome/renderer/prerender/prerender_webmediaplayer.h"
+
+#include "chrome/common/render_messages.h"
+#include "content/renderer/render_view.h"
+#include "media/base/filter_collection.h"
+#include "media/base/media_log.h"
+#include "media/base/pipeline_impl.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebURL.h"
+
+namespace prerender {
+
+PrerenderWebMediaPlayer::PrerenderWebMediaPlayer(
+    RenderView* render_view,
+    WebKit::WebMediaPlayerClient* client,
+    media::FilterCollection* collection,
+    media::MessageLoopFactory* message_loop_factory,
+    webkit_glue::MediaStreamClient* media_stream_client,
+    media::MediaLog* media_log)
+  : RenderViewObserver(render_view),

[scherkus (not reviewing), 2011/10/03 18:19:45]

indent by 2 more spaces

[Shishir, 2011/10/04 23:02:39]

Done.

+    WebMediaPlayerImpl(client,
+                       collection,
+                       message_loop_factory,
+                       media_stream_client,
+                       media_log),
+    is_prerendering_(true),
+    should_play_(false) {
+}
+
+PrerenderWebMediaPlayer::~PrerenderWebMediaPlayer() {

[scherkus (not reviewing), 2011/10/03 18:19:45]

nit: collapse empty methods to {}

[Shishir, 2011/10/04 23:02:39]

Done.

+}
+
+void PrerenderWebMediaPlayer::load(const WebKit::WebURL& url) {
+  if (is_prerendering_) {
+    url_to_load_.reset(new WebKit::WebURL(url));
+    return;
+  }
+  WebMediaPlayerImpl::load(url);
+}
+
+void PrerenderWebMediaPlayer::cancelLoad() {
+  if (is_prerendering_) {
+    url_to_load_.reset(NULL);
+    return;
+  }
+  WebMediaPlayerImpl::cancelLoad();
+}
+
+void PrerenderWebMediaPlayer::play() {

[scherkus (not reviewing), 2011/10/03 18:19:45]

is it possible to receive play if we never finish loading?

it's hard to tell from WebKit's HTMLMediaElement.cpp code whether it'll wait to
call play() until we've called back from the load() with an update to
network/ready state

[Shishir, 2011/10/04 23:02:39]

Looks like you are correct. I dug into the webkit code and it seems to be using
the states to determine when to play. removed.

On 2011/10/03 18:19:45, scherkus wrote:

+  if (is_prerendering_) {
+    should_play_ = true;
+    return;
+  }
+  WebMediaPlayerImpl::play();
+}
+
+void PrerenderWebMediaPlayer::pause() {

[scherkus (not reviewing), 2011/10/03 18:19:45]

ditto

[Shishir, 2011/10/04 23:02:39]

removed.

+  if (is_prerendering_) {
+    should_play_ = false;
+    return;
+  }
+  WebMediaPlayerImpl::pause();
+}
+
+bool PrerenderWebMediaPlayer::OnMessageReceived(const IPC::Message& message) {
+  IPC_BEGIN_MESSAGE_MAP(PrerenderWebMediaPlayer, message)
+    IPC_MESSAGE_HANDLER(ChromeViewMsg_SetIsPrerendering, OnSetIsPrerendering)
+  IPC_END_MESSAGE_MAP()
+
+  return false;
+}
+
+void PrerenderWebMediaPlayer::OnSetIsPrerendering(bool is_prerendering) {
+  // Prerendering can only be enabled prior to a RenderView's first
+  // navigation, so no PrerenderWebMediaPlayer should see the notification
+  // that enables prerendering.

[scherkus (not reviewing), 2011/10/03 18:19:45]

I haven't looked at prerendering before, but why have a SetIsPrerendering if it
can only ever be set to false?

[Shishir, 2011/10/04 23:02:39]

It can be set to true. The argument here is that it should have been set to true
much before this class can be instantiated. So this class should never receive a
notification of "true".

+  DCHECK(!is_prerendering);
+  if (is_prerendering_ && !is_prerendering) {
+    is_prerendering_ = false;
+    load(*url_to_load_);

[scherkus (not reviewing), 2011/10/03 18:19:45]

is it possible to have this IPC called before we get a load()?

in that case url_to_load_ would be NULL

[Shishir, 2011/10/04 23:02:39]

Thanks for the catch. Fixed.

+    if (should_play_)
+      play();
+  }
+}
+
+} // namespace prerender