Add prompt and confirm client functions to WebKit2

Reviewed by Anders Carlsson.

WebKit2: 

* Shared/CoreIPCSupport/WebPageProxyMessageKinds.h:
(WebPageProxyMessage::):
* UIProcess/API/C/WKPage.h:
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::didReceiveSyncMessage):
(WebKit::WebPageProxy::runJavaScriptAlert):
(WebKit::WebPageProxy::runJavaScriptConfirm):
(WebKit::WebPageProxy::runJavaScriptPrompt):
* UIProcess/WebPageProxy.h:
* UIProcess/WebUIClient.cpp:
(WebKit::WebUIClient::runJavaScriptAlert):
(WebKit::WebUIClient::runJavaScriptConfirm):
(WebKit::WebUIClient::runJavaScriptPrompt):
* UIProcess/WebUIClient.h:
* WebKit2.xcodeproj/project.pbxproj:
* WebProcess/WebCoreSupport/WebChromeClient.cpp:
(WebKit::WebChromeClient::runJavaScriptConfirm):
(WebKit::WebChromeClient::runJavaScriptPrompt):

WebKitTools: 

* MiniBrowser/mac/BrowserWindowController.m:
(-[BrowserWindowController awakeFromNib]):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@64065 268f45cc-cd09-0410-ab3c-d52691b4dbfc