[Navigation] Support download navigations

https://bugs.webkit.org/show_bug.cgi?id=272349

Reviewed by Alex Christensen.

Implement detecting download requests and firing a navigate event for them [1].

[1] https://html.spec.whatwg.org/multipage/nav-history-apis.html#fire-a-download-request-navigate-event

* LayoutTests/TestExpectations:
* LayoutTests/imported/w3c/web-platform-tests/navigation-api/navigate-event/navigate-anchor-download-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/navigation-api/navigate-event/navigate-anchor-download-userInitiated-expected.txt:
* LayoutTests/imported/w3c/web-platform-tests/navigation-api/ordering-and-transition/anchor-download-expected.txt:
* Source/WebCore/loader/PolicyChecker.cpp:
(WebCore::FrameLoader::PolicyChecker::checkNavigationPolicy):
* Source/WebCore/page/Navigation.cpp:
(WebCore::Navigation::dispatchDownloadNavigateEvent):

Canonical link: https://commits.webkit.org/278950@main

LayoutTests/imported/w3c/web-platform-tests/navigation-api/navigate-event/navigate-anchor-download-expected.txt

@@ -1,8 +1,6 @@
 
-Harness Error (TIMEOUT), message = null
-
-TIMEOUT <a> fires navigate and populates downloadRequest with '' Test timed out
-TIMEOUT <a> fires navigate and populates downloadRequest with 'filename' Test timed out
-TIMEOUT <area> fires navigate and populates downloadRequest with '' Test timed out
-TIMEOUT <area> fires navigate and populates downloadRequest with 'filename' Test timed out
+PASS <a> fires navigate and populates downloadRequest with ''
+PASS <a> fires navigate and populates downloadRequest with 'filename'
+PASS <area> fires navigate and populates downloadRequest with ''
+PASS <area> fires navigate and populates downloadRequest with 'filename'
 

LayoutTests/imported/w3c/web-platform-tests/navigation-api/navigate-event/navigate-anchor-download-userInitiated-expected.txt

@@ -1,6 +1,4 @@
 Click me
 
-Harness Error (TIMEOUT), message = null
-
-TIMEOUT <a download> click fires navigate event Test timed out
+PASS <a download> click fires navigate event
 

LayoutTests/imported/w3c/web-platform-tests/navigation-api/ordering-and-transition/anchor-download-expected.txt

@@ -1,4 +1,4 @@
 
 
-FAIL <a download> fires navigate, but not navigatesuccess or navigateerror when not intercepted by intercept() assert_true: expected true got false
+PASS <a download> fires navigate, but not navigatesuccess or navigateerror when not intercepted by intercept()
 

Source/WebCore/loader/PolicyChecker.cpp

@@ -50,6 +50,7 @@
 #include "LocalFrame.h"
 #include "LocalFrameLoaderClient.h"
 #include "Logging.h"
+#include "Navigation.h"
 #include "ThreadableBlobRegistry.h"
 #include "URLKeepingBlobAlive.h"
 #include <wtf/CompletionHandler.h>
@@ -206,6 +207,15 @@ void PolicyChecker::checkNavigationPolicy(ResourceRequest&& request, const Resou
     bool isInitialEmptyDocumentLoad = !frameLoader->stateMachine().committedFirstRealDocumentLoad() && request.url().protocolIsAbout() && !substituteData.isValid();
     m_delegateIsDecidingNavigationPolicy = true;
     String suggestedFilename = action.downloadAttribute().isEmpty() ? nullAtom() : action.downloadAttribute();
+    if (!action.downloadAttribute().isNull()) {
+        RefPtr document = frame->document();
+        if (document && document->settings().navigationAPIEnabled()) {
+            if (RefPtr domWindow = document->domWindow()) {
+                if (!domWindow->protectedNavigation()->dispatchDownloadNavigateEvent(request.url(), action.downloadAttribute()))
+                    return function({ }, nullptr, NavigationPolicyDecision::IgnoreLoad);
+            }
+        }
+    }
     FramePolicyFunction decisionHandler = [
         this,
         weakThis = WeakPtr { *this },

Source/WebCore/page/Navigation.cpp

@@ -669,11 +669,10 @@ bool Navigation::dispatchPushReplaceReloadNavigateEvent(const URL& url, Navigati
 }
 
 // https://html.spec.whatwg.org/multipage/nav-history-apis.html#fire-a-download-request-navigate-event
-bool Navigation::dispatchDownloadNavigateEvent(const URL&, const String& downloadFilename)
+bool Navigation::dispatchDownloadNavigateEvent(const URL& url, const String& downloadFilename)
 {
-    // FIXME
-    UNUSED_PARAM(downloadFilename);
-    return false;
+    Ref destination = NavigationDestination::create(url, nullptr, false);
+    return innerDispatchNavigateEvent(NavigationNavigationType::Push, WTFMove(destination), downloadFilename);
 }
 
 } // namespace WebCore