browser(firefox): allow loading file URLs in web process (#1110)

browser_patches/firefox/BUILD_NUMBER

@@ -1 +1 @@
-1029
+1030

browser_patches/firefox/preferences/playwright.cfg

@@ -22,6 +22,9 @@ pref("browser.newtabpage.enabled", false);
 // Do not redirect user when a milstone upgrade of Firefox is detected
 pref("browser.startup.homepage_override.mstone", "ignore");
 
+pref("browser.tabs.remote.separateFileUriProcess", false);
+pref("security.sandbox.content.level", 2);
+
 // Disable topstories
 pref("browser.newtabpage.activity-stream.feeds.section.topstories", false);
 // DevTools JSONViewer sometimes fails to load dependencies with its require.js.