Avoid unnecessarily constructing PlatformMediaSessionManager on Document destruction

[Chris Dumez]

When looking at a benchmark trace, I saw the following:
54,16.2%,15.5%,WebCore::HTMLDocument::~HTMLDocument() (in WebCore)
54,16.2%,15.5%,    WebCore::Document::~Document() (in WebCore)
54,16.2%,15.5%,        WebCore::PlatformMediaSessionManager::sharedManager() (in WebCore)
54,16.2%,15.5%,            WebCore::MediaSessionManageriOS::MediaSessionManageriOS() (in WebCore)
54,16.2%,15.5%,                -[WebMediaSessionHelper initWithCallback:] (in WebCore)
54,16.2%,15.5%,                    -[WebMediaSessionHelper allocateVolumeView] (in WebCore)
50,15.0%,14.4%,                        -[MPVolumeView initWithFrame:style:] (in MediaPlayer)
4,1.2%,1.2%,                        initMPVolumeView() (in WebCore)

We end up constructing a PlatformMediaSessionManager when destroying a Document, because of a call to PlatformMediaSessionManager::shared().stopAllMediaPlaybackForProcess(). This seems unfortunate.

[Chris Dumez]

Created attachment 257730 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 257730 [details]
Patch

Clearing flags on attachment: 257730

Committed r187544: <http://trac.webkit.org/changeset/187544>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.