Reviewed by Timothy Hatcher.

        Extract PageGroupLoadDeferrer from Chrome.cpp

        * GNUmakefile.am: added PageGroupLoadDeferrer
        * WebCore.pro: ditto
        * WebCore.scons: ditto
        * WebCore.vcproj/WebCore.vcproj: ditto
        * WebCore.xcodeproj/project.pbxproj: ditto
        * WebCoreSources.bkl: ditto
        * page/Chrome.cpp: PageGroupLoadDeferrer impl moved to a separate class.
        * page/PageGroupLoadDeferrer.cpp: Added.
        (WebCore::PageGroupLoadDeferrer::PageGroupLoadDeferrer):
        (WebCore::PageGroupLoadDeferrer::~PageGroupLoadDeferrer):
        * page/PageGroupLoadDeferrer.h: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@43010 268f45cc-cd09-0410-ab3c-d52691b4dbfc