[iOS][WK2] PDFs never load inline again after the Web process crashes

[iOS][WK2] PDFs never load inline again after the Web process crashes
https://bugs.webkit.org/show_bug.cgi?id=134432
<rdar://problem/17484205>

Reviewed by Dan Bernstein.

After a crash, the WebPage never gets mimeTypesWithCustomContentProviders filled back in.

* Shared/WebPageCreationParameters.cpp:
(WebKit::WebPageCreationParameters::encode):
(WebKit::WebPageCreationParameters::decode):
* Shared/WebPageCreationParameters.h:
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::creationParameters):
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::WebPage):
Add mimeTypesWithCustomContentProviders to WebPageCreationParameters.

* UIProcess/Cocoa/WKWebViewContentProviderRegistry.h:
* UIProcess/Cocoa/WKWebViewContentProviderRegistry.mm:
(-[WKWebViewContentProviderRegistry addPage:]):
We don't need to send the MIME types across when a page is added, because it already got them in its creation parameters.

(-[WKWebViewContentProviderRegistry removePage:]):
(-[WKWebViewContentProviderRegistry _mimeTypesWithCustomContentProviders]):
Return a vector of all registered MIME types.

* UIProcess/ios/PageClientImplIOS.h:
* UIProcess/ios/PageClientImplIOS.mm:
(WebKit::PageClientImpl::mimeTypesWithCustomContentProviders):
* UIProcess/PageClient.h:
Add (iOS only for now) mimeTypesWithCustomContentProviders to PageClient.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@170570 268f45cc-cd09-0410-ab3c-d52691b4dbfc