Add really basic BackForwardList support.

Reviewed by Anders Carlsson.

* Shared/CoreIPCSupport/WebPageMessageKinds.h:
(WebPageMessage::):
Add new message kind.

* Shared/CoreIPCSupport/WebPageProxyMessageKinds.h:
(WebPageProxyMessage::):
Add new message kinds. Remove DidChangeCanGoBack and DidChangeCanGoForward.

* UIProcess/API/C/WKPage.cpp:
(WKPageGoToBackForwardListItem):
* UIProcess/API/C/WKPage.h:
Add function to initiate a navigation to a BackForward item.  The
BackForward list will be updated to use this as the current item
asynchronously. 

* UIProcess/WebBackForwardList.cpp:
(WebKit::WebBackForwardList::WebBackForwardList):
(WebKit::WebBackForwardList::addItem): Added.
(WebKit::WebBackForwardList::goToItem): Added.
(WebKit::WebBackForwardList::itemAtIndex): Added.
(WebKit::WebBackForwardList::backListCount): Changed to return int matching WebCore.
(WebKit::WebBackForwardList::forwardListCount): Ditto.
(WebKit::WebBackForwardList::backListWithLimit): Add cast to int.
(WebKit::WebBackForwardList::forwardListWithLimit): Ditto.
(WebKit::WebBackForwardList::backListAsImmutableArrayWithLimit): Ditto.
(WebKit::WebBackForwardList::forwardListAsImmutableArrayWithLimit): Ditto.
* UIProcess/WebBackForwardList.h:

* UIProcess/WebBackForwardListItem.cpp:
(WebKit::WebBackForwardListItem::WebBackForwardListItem):
* UIProcess/WebBackForwardListItem.h:
(WebKit::WebBackForwardListItem::create):
(WebKit::WebBackForwardListItem::itemID):
Added itemID.

* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::WebPageProxy):
(WebKit::WebPageProxy::close):
(WebKit::WebPageProxy::canGoForward):
(WebKit::WebPageProxy::canGoBack):
(WebKit::WebPageProxy::goToBackForwardItem):
(WebKit::WebPageProxy::didReceiveMessage):
(WebKit::WebPageProxy::didReceiveSyncMessage):
(WebKit::WebPageProxy::addItemToBackForwardList):
(WebKit::WebPageProxy::goToItemInBackForwardList):
(WebKit::WebPageProxy::processDidExit):
* UIProcess/WebPageProxy.h:
- Removed m_canGoBack and m_canGoForward booleans and instead use the BackForwardList.
- Forward goToBackForwardItem to the WebProcess.
- Respond to messages from the WebBackForwardListProxy in the WebProcess,
  forwarding to the WebBackForwardList.

* WebProcess/WebCoreSupport/WebBackForwardControllerClient.cpp:
(WebKit::WebBackForwardControllerClient::createBackForwardList):
Start using a WebBackForwardListProxy instead of a BackForwardListImpl.

* WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
(WebKit::WebFrameLoaderClient::dispatchDidAddBackForwardItem):
(WebKit::WebFrameLoaderClient::dispatchDidRemoveBackForwardItem):
(WebKit::WebFrameLoaderClient::dispatchDidChangeBackForwardIndex):
Remove calls backForwardListDidChange() now that we communicate much more
information than just this state.

* WebProcess/WebPage/WebBackForwardListProxy.cpp:
(WebKit::idToHistoryItemMap):
(WebKit::historyItemToIDMap):
(WebKit::generateHistoryItemID):
(WebKit::getIDForHistoryItem):
(WebKit::WebBackForwardListProxy::itemForID):
Add leaking cached maps of HistoryItems to IDs, the life time of these
objects will be improved in a subsequent patch.

(WebKit::WebBackForwardListProxy::WebBackForwardListProxy):
(WebKit::WebBackForwardListProxy::addItem):
(WebKit::WebBackForwardListProxy::goBack):
(WebKit::WebBackForwardListProxy::goForward):
(WebKit::WebBackForwardListProxy::goToItem):
(WebKit::WebBackForwardListProxy::backItem):
(WebKit::WebBackForwardListProxy::currentItem):
(WebKit::WebBackForwardListProxy::forwardItem):
(WebKit::WebBackForwardListProxy::itemAtIndex):
(WebKit::WebBackForwardListProxy::backListWithLimit):
(WebKit::WebBackForwardListProxy::forwardListWithLimit):
(WebKit::WebBackForwardListProxy::capacity):
(WebKit::WebBackForwardListProxy::setCapacity):
(WebKit::WebBackForwardListProxy::enabled):
(WebKit::WebBackForwardListProxy::setEnabled):
(WebKit::WebBackForwardListProxy::backListCount):
(WebKit::WebBackForwardListProxy::forwardListCount):
(WebKit::WebBackForwardListProxy::containsItem):
(WebKit::WebBackForwardListProxy::close):
(WebKit::WebBackForwardListProxy::closed):
(WebKit::WebBackForwardListProxy::removeItem):
(WebKit::WebBackForwardListProxy::entries):
(WebKit::WebBackForwardListProxy::pushStateItem):
* WebProcess/WebPage/WebBackForwardListProxy.h:
Forward functions to the UIProcess.

* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::goToBackForwardItem):
(WebKit::WebPage::didReceiveMessage):
* WebProcess/WebPage/WebPage.h:
Respond to GoToBackForwardItem message.

* mac/WebKit2.exp: Add new API function.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@62996 268f45cc-cd09-0410-ab3c-d52691b4dbfc