Remove unused VisibleContentRectUpdateInfo update ID

Remove unused VisibleContentRectUpdateInfo update ID
https://bugs.webkit.org/show_bug.cgi?id=133777

Reviewed by Benjamin Poulain.

Remove some unused code.

* Shared/VisibleContentRectUpdateInfo.cpp:
(WebKit::VisibleContentRectUpdateInfo::encode):
(WebKit::VisibleContentRectUpdateInfo::decode):
* Shared/VisibleContentRectUpdateInfo.h:
(WebKit::VisibleContentRectUpdateInfo::VisibleContentRectUpdateInfo):
(WebKit::operator==):
(WebKit::VisibleContentRectUpdateInfo::updateID): Deleted.
* Shared/mac/RemoteLayerTreeTransaction.h:
(WebKit::RemoteLayerTreeTransaction::setLastVisibleContentRectUpdateID): Deleted.
(WebKit::RemoteLayerTreeTransaction::lastVisibleContentRectUpdateID): Deleted.
* Shared/mac/RemoteLayerTreeTransaction.mm:
(WebKit::RemoteLayerTreeTransaction::encode):
(WebKit::RemoteLayerTreeTransaction::decode):
* UIProcess/WebPageProxy.h:
(WebKit::WebPageProxy::nextVisibleContentRectUpdateID): Deleted.
(WebKit::WebPageProxy::lastVisibleContentRectUpdateID): Deleted.
* UIProcess/ios/WKContentView.mm:
(-[WKContentView didUpdateVisibleRect:unobscuredRect:unobscuredRectInScrollViewCoordinates:scale:minimumScale:inStableState:isChangingObscuredInsetsInteractively:]):
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::WebPage):
(WebKit::WebPage::willCommitLayerTree):
* WebProcess/WebPage/WebPage.h:
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::updateVisibleContentRects):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@169863 268f45cc-cd09-0410-ab3c-d52691b4dbfc