REGRESSION (r229828): Facebook login popup is blank

REGRESSION (r229828): Facebook login popup is blank
https://bugs.webkit.org/show_bug.cgi?id=184206
<rdar://problem/39057006>

Reviewed by Wenson Hsieh.

Source/WebCore:

Since r229828, we freeze the layer tree during the navigation policy check.
We freeze in WebFrameLoaderClient::dispatchDecidePolicyForNavigationAction()
and unfreeze in WebFrameLoaderClient::didDecidePolicyForNavigationAction().

WebFrameLoaderClient::dispatchDecidePolicyForNavigationAction() gets called
from PolicyChecker::checkNavigationPolicy() which has 3 call sites in
FrameLoader and one in DocumentLoader for redirects. The call sites in
FrameLoader were taking care of calling didDecidePolicyForNavigationAction()
on the FrameLoaderClient in their completion handler, but the DocumentLoader
call site was failing to do so. As a result, the layer tree would stay frozen.

To make this a lot less error prone, I moved the call to
WebFrameLoaderClient::didDecidePolicyForNavigationAction() to
PolicyChecker::checkNavigationPolicy(), inside the completion handler passed
to WebFrameLoaderClient::dispatchDecidePolicyForNavigationAction(). This way,
even if new code starts calling PolicyChecker::checkNavigationPolicy(), we
do not need to worry about letting the client know when the policy decision
is made.

No new tests, covered by existing redirection tests with the
new assertion I added.

* loader/FrameLoader.cpp:
(WebCore::FrameLoader::continueFragmentScrollAfterNavigationPolicy):
(WebCore::FrameLoader::continueLoadAfterNavigationPolicy):
* loader/PolicyChecker.cpp:
(WebCore::PolicyChecker::checkNavigationPolicy):

Source/WebKit:

Add assertion to make sure we never try to do a policy check to
a resource response while a policy check for a navigation is
pending. This assertion was being hit by several of our redirection
tests without my fix.

* WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
(WebKit::WebFrameLoaderClient::dispatchDecidePolicyForResponse):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@230128 268f45cc-cd09-0410-ab3c-d52691b4dbfc