died at least once
https://bugs.webkit.org/show_bug.cgi?id=52730

Reviewed by Darin Adler.

WebDatabaseManagerProxy::invalidate was setting m_webContext to 0, and invalidate gets
called in WebContext::processDidClose. However, m_webContext is only set in the
constructor, which is only called from the constructor of WebContext, so attempting to send
a message to any new WebProcess after the first one died was causing a null deref.

This patch moves setting m_webcontext into clearContext and clearContext is only called in
the WebContext destructor.

This patch also adds checks for a valid WebProcessProxy before attempting to send messages to
the WebProcessProxy so that if the WebProcess has died and has not been revived, it does not
attempt to dereference a null WebProcessProxy.

* UIProcess/WebContext.cpp:
(WebKit::WebContext::~WebContext):
Call WebDatabaseManagerProxy::clearContext.
* UIProcess/WebContext.h:
(WebKit::WebContext::hasValidProcess):
Make this method public so that it can be called from WebDatabaseManagerProxy.

* UIProcess/WebDatabaseManagerProxy.cpp:
(WebKit::WebDatabaseManagerProxy::getDatabasesByOrigin):
If there isn't a valid process, invalidate the callback and return early.
(WebKit::WebDatabaseManagerProxy::getDatabaseOrigins):
Ditto.
(WebKit::WebDatabaseManagerProxy::deleteDatabaseWithNameForOrigin):
If tehre isn't a valid process return early.
(WebKit::WebDatabaseManagerProxy::deleteDatabasesForOrigin):
Ditto.
(WebKit::WebDatabaseManagerProxy::deleteAllDatabases):
Ditto.
(WebKit::WebDatabaseManagerProxy::setQuotaForOrigin):
Ditto.
(WebKit::WebDatabaseManagerProxy::invalidate):
Move setting m_webContext to 0 from here ...
* UIProcess/WebDatabaseManagerProxy.h:
(WebKit::WebDatabaseManagerProxy::clearContext):
... to here.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76163 268f45cc-cd09-0410-ab3c-d52691b4dbfc