<https://webkit.org/b/119853> REGRESSION (r139343): WebKit crashes when canceling...

<https://webkit.org/b/119853> REGRESSION (r139343): WebKit crashes when canceling a load inside webView:resource:didFinishLoadingFromDataSource:

Reviewed by Brady Eidson.

Source/WebCore:

A client implementing webView:resource:didFinishLoadingFromDataSource:
might decide to call stopLoading: for the identifier that just finished
loading. If this happens we re-enter the loader and attempt to cancel a
load that has already finished and been removed from the set of active
loaders. Prevent this by clearing DocumentLoader's
m_identifierForLoadWithoutResourceLoader before calling
dispatchDidFinishLoading().

New API test: WebKit1.StopLoadingFromDidFinishLoading.

* loader/DocumentLoader.cpp:
(WebCore::DocumentLoader::finishedLoading): Set
m_identifierForLoadWithoutResourceLoader to 0 before calling
dispatchDidFinishLoading().

Tools:

Wrote an API test that verifies -[WebView stopLoading:] can be called
inside webView:resource:didFinishLoadingFromDataSource: without crashing.

* TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj:
* TestWebKitAPI/Tests/mac/StopLoadingFromDidFinishLoading.mm: Added.
(-[StopLoadingFromDidFinishLoadingDelegate webView:resource:didFinishLoadingFromDataSource:]):
(TestWebKitAPI::TEST):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@154115 268f45cc-cd09-0410-ab3c-d52691b4dbfc