[WK2] Call LayerTreeHost::deviceOrPageScaleFactorChanged() when a device or page scale factor is changed.
https://bugs.webkit.org/show_bug.cgi?id=107802

Patch by Huang Dongsung <luxtella@company100.net> on 2013-01-29
Reviewed by Simon Fraser.

Currently, LayerTreeHostMac and *GTK call deviceOrPageScaleFactorChanged()
of the non compositing GraphicsLayer when a device scale factor is changed.

There are two problems.
1. We don't notify LayerTreeHost when a page scale factor is changed.
2. When using TiledCoreAnimationDrawingAreaProxy, LayerTreeHostMac does
not receive the device scale factor changed callback.

So this patch changes three points.
1. Rename from deviceScaleFactorDidChange() to deviceOrPageScaleFactorChanged()
in LayerTreeHost.
2. WebPage::setDeviceScaleFactor() calls LayerTreeHost::deviceScaleFactorDidChange()
because of dealing with TiledCoreAnimationDrawingAreaProxy.
3. WebPage::pageScaleFactor() calls LayerTreeHost::deviceScaleFactorDidChange()
to call deviceOrPageScaleFactorChanged() of the non compositing GraphicsLayer.

Unfortunately, I couldn't think of a way to test this in an automated fashion.

* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.h:
(WebKit::CoordinatedLayerTreeHost::deviceOrPageScaleFactorChanged):
* WebProcess/WebPage/DrawingAreaImpl.cpp:
(WebKit::DrawingAreaImpl::updateBackingStoreState):
    Don't call LayerTreeHost::deviceScaleFactorDidChange() because this
    method calls WebPage::setDeviceScaleFactor() and then
    LayerTreeHost::deviceScaleFactorDidChange() is called.
* WebProcess/WebPage/LayerTreeHost.h:
(LayerTreeHost):
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::scalePage):
(WebKit::WebPage::setDeviceScaleFactor):
* WebProcess/WebPage/gtk/LayerTreeHostGtk.cpp:
(WebKit::LayerTreeHostGtk::deviceOrPageScaleFactorChanged):
* WebProcess/WebPage/gtk/LayerTreeHostGtk.h:
(LayerTreeHostGtk):
* WebProcess/WebPage/mac/LayerTreeHostMac.h:
(LayerTreeHostMac):
* WebProcess/WebPage/mac/LayerTreeHostMac.mm:
(WebKit::LayerTreeHostMac::deviceOrPageScaleFactorChanged):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141171 268f45cc-cd09-0410-ab3c-d52691b4dbfc