Fix build break on EFL and GTK ports since r170611 and r170614
https://bugs.webkit.org/show_bug.cgi?id=134479

Reviewed by Carlos Garcia Campos.

Add LegacySessionStateCodingNone.cpp in order to fix build break on EFL and GTK ports. Additionally
SessionStateConversion.cpp is added to CMakeLists.txt as well.

* CMakeLists.txt:
* UIProcess/LegacySessionStateCoding.h: Copied from Source/WebKit2/UIProcess/mac/LegacySessionStateCoding.h.
* UIProcess/LegacySessionStateCodingNone.cpp: Renamed from Source/WebKit2/UIProcess/mac/LegacySessionStateCoding.h.
(WebKit::encodeLegacySessionHistoryEntryData):
(WebKit::decodeLegacySessionState):
(WebKit::decodeLegacySessionHistoryEntryData):
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::loadFile):
(WebKit::WebPageProxy::restoreFromState):
* WebKit2.xcodeproj/project.pbxproj:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170631 268f45cc-cd09-0410-ab3c-d52691b4dbfc
[WK2] Can not convert ‘sessionState.WebKit::SessionState::provisionalURL’ from ‘WebCore::URL’ to ‘bool’
https://bugs.webkit.org/show_bug.cgi?id=134487

Rubber-stamped by Carlos Garcia Campos.

* UIProcess/WebPageProxy.cpp: Use isNull().
(WebKit::WebPageProxy::restoreFromState):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170632 268f45cc-cd09-0410-ab3c-d52691b4dbfc