[watchOS] Turning on lockdown mode should not cause certain web fonts…

… to be enabled

https://bugs.webkit.org/show_bug.cgi?id=259791
rdar://112281112

Reviewed by Aditya Keerthi.

To optimize performance and data use, web fonts are currently always disabled on watchOS. However,
enabling lockdown mode on watchOS actually causes us to *enable* support for a small subset for web
fonts, since we change `DownloadableBinaryFontAllowedTypes` state from `None` (i.e. no web fonts
allowed at all) to `Restricted`. This subsequently causes cached fonts in the GPU process to end up
in an unexpected state on watchOS, triggering a `MESSAGE_CHECK` and causing the web process to
terminate.

It doesn't make sense for Lockdown mode to make web fonts *less* restrictive, so we can simply fix
this by maintaining `DownloadableBinaryFontAllowedTypes::None` in the case where web fonts are
already unconditionally disabled.

* Source/WebKit/WebProcess/WebPage/WebPage.cpp:
(WebKit::adjustSettingsForLockdownMode):
* Tools/TestWebKitAPI/Tests/WebKitCocoa/LockdownModeFonts.mm:

Rebaseline an API test for compatibility with watchOS as well, where web fonts are always disabled.

Canonical link: https://commits.webkit.org/266563@main

Source/WebKit/WebProcess/WebPage/WebPage.cpp

@@ -4461,7 +4461,14 @@ static void adjustSettingsForLockdownMode(Settings& settings, const WebPreferenc
 #if ENABLE(WEB_AUDIO)
     settings.setWebAudioEnabled(false);
 #endif
-    settings.setDownloadableBinaryFontAllowedTypes(DownloadableBinaryFontAllowedTypes::Restricted);
+    switch (settings.downloadableBinaryFontAllowedTypes()) {
+    case DownloadableBinaryFontAllowedTypes::Any:
+        settings.setDownloadableBinaryFontAllowedTypes(DownloadableBinaryFontAllowedTypes::Restricted);
+        break;
+    case DownloadableBinaryFontAllowedTypes::Restricted:
+    case DownloadableBinaryFontAllowedTypes::None:
+        break;
+    }
 #if ENABLE(WEB_CODECS)
     settings.setWebCodecsEnabled(false);
     settings.setWebCodecsAV1Enabled(false);

Tools/TestWebKitAPI/Tests/WebKitCocoa/LockdownModeFonts.mm

@@ -157,7 +157,11 @@
         auto targetResult = static_cast<NSNumber *>([webView objectByEvaluatingJavaScript:@"target.offsetWidth"]).intValue;
         auto referenceResult = static_cast<NSNumber *>([webView objectByEvaluatingJavaScript:@"reference.offsetWidth"]).intValue;
 
+#if PLATFORM(WATCHOS)
+        EXPECT_NE(targetResult, referenceResult);
+#else
         EXPECT_EQ(targetResult, referenceResult);
+#endif
     }
 }
 }