[TexMap][Qt] Start PageClientQ[Graphics]Widget::syncTimer only when the syncTimer

[TexMap][Qt] Start PageClientQ[Graphics]Widget::syncTimer only when the syncTimer
is inactive.
https://bugs.webkit.org/show_bug.cgi?id=70407

Make sure we only activate the synchronization timer in
PageClientQWidget/PageClientQGraphicsWidget if it's not already active,
otherwise syncLayers may be called redundantly.

Patch by Huang Dongsung <luxtella@company100.net> on 2011-11-15
Reviewed by Noam Rosenthal.

* WebCoreSupport/PageClientQt.cpp:
(WebCore::PageClientQWidget::markForSync):
(WebCore::PageClientQWidget::syncLayers):
(WebCore::PageClientQGraphicsWidget::syncLayers):
(WebCore::PageClientQGraphicsWidget::markForSync):
* WebCoreSupport/PageClientQt.h:
(WebCore::PageClientQGraphicsWidget::PageClientQGraphicsWidget):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@100410 268f45cc-cd09-0410-ab3c-d52691b4dbfc