This gets the video on the front page of vimeo.com painting (though
you can't make it play because we don't support mouse events yet).

Fixes <http://webkit.org/b/44274> <rdar://problem/8330398> Windowless
plugins don't paint in WebKit2 on Windows

Reviewed by Sam Weinig.

* WebProcess/Plugins/Netscape/NetscapeBrowserFuncs.cpp:
(WebKit::NPN_GetValue): Tell the plugin that we support windowless
mode on Windows.
(WebKit::NPN_SetValue): Implemented handling of NPPVpluginWindowBool
by calling through to NetscapePlugin::setIsWindowed.

* WebProcess/Plugins/Netscape/NetscapePlugin.cpp:
(WebKit::NetscapePlugin::NetscapePlugin): Added initialization of
m_isWindowed. It defaults to false on Mac and true on other platforms,
matching WebCore's PluginView.

* WebProcess/Plugins/Netscape/NetscapePlugin.h: Added m_isWindowed.
(WebKit::NetscapePlugin::setIsWindowed): Added standard setter.

* WebProcess/Plugins/Netscape/mac/NetscapePluginMac.mm:
(WebKit::NetscapePlugin::platformPaint): Moved Mac-specific context
translation code here from PluginView::paint.

* WebProcess/Plugins/Netscape/win/NetscapePluginWin.cpp:
(WebKit::NetscapePlugin::platformPaint): Implemented. Code was ported
from WebCore's PluginViewWin.cpp.

* WebProcess/Plugins/Plugin.h: Updated the comment for Plugin::paint
to explain the coordinate system of the context.

* WebProcess/Plugins/PluginView.cpp:
(WebKit::PluginView::paint): Changed to translate the context from
document to window coordinates. We were previously trying to translate
to plugin-local coordinates, but this only worked for documents whose
origin was the same as the window's origin (i.e., the main frame). The
plugin takes care of any further translations needed. (Mac translates
the context into plugin-local coordinates, and Windows leaves it in
window coordinates.)

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@65705 268f45cc-cd09-0410-ab3c-d52691b4dbfc