https://bugs.webkit.org/show_bug.cgi?id=123379

Reviewed by Darin Adler.

Visibility state of the Page should be stored and communicated consistently.

Remove individual visibility flags from WebPageProxy, WebPageCreationParameters,
and replace them with a ViewState, and add a ViewState member to WebPage.
Merge together all messages that convey and individual aspect of the ViewState.

Restructure WebPageProxy::viewStateDidChange to break the operation down into
three steps: 1) update m_viewState, 2) send the new ViewState to the WebProcess,
and 3) perform any further work necessary in the UIProcess.

This patch fixes a problem that if the web process crashes m_isVisible &
m_isInWindow in WebPageProxy were not updated, and could have held stale values
on reattach.

In WebPage, add a new message to update the entire ViewState - diff the prior
value against the new one to detect changes, call existing methods accordingly.

* Shared/ViewState.h:
    - Add constants 'Reset', 'AllFlags'
* Shared/WebPageCreationParameters.cpp:
(WebKit::WebPageCreationParameters::encode):
(WebKit::WebPageCreationParameters::decode):
* Shared/WebPageCreationParameters.h:
    - Removed boolean visibility flags, added viewState.
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::WebPageProxy):
    - Constructor calls updateViewState to initialize m_viewState.
(WebKit::WebPageProxy::reattachToWebProcess):
    - ViewStaet is not updated while detatched; recalculate.
(WebKit::WebPageProxy::initializeWebPage):
    - m_isVisible -> isViewVisible()
(WebKit::WebPageProxy::updateViewState):
    - Added, update m_viewState by querying the page client.
(WebKit::WebPageProxy::viewStateDidChange):
    - Restructured to use m_viewState, reordered to combine messages.
(WebKit::WebPageProxy::creationParameters):
    - Removed boolean visibility flags, added viewState.
* UIProcess/WebPageProxy.h:
(WebKit::WebPageProxy::isInWindow):
(WebKit::WebPageProxy::isViewVisible):
    - Removed boolean visibility flags, added viewState.
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::WebPage):
    - initial state now passed as a ViewState.
(WebKit::WebPage::setIsInWindow):
    - Remove code to send reply (this is handled by setViewState).
(WebKit::WebPage::setViewState):
    - Set m_viewState - diff from prior & call methods to update.
* WebProcess/WebPage/WebPage.h:
    - Added setViewState, m_viewState.
* WebProcess/WebPage/WebPage.messages.in:
    - Add SetViewState, remove individual messages.
* WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm:
(WebKit::TiledCoreAnimationDrawingArea::TiledCoreAnimationDrawingArea):
    - initial state now passed as a ViewState.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158372 268f45cc-cd09-0410-ab3c-d52691b4dbfc