Remove command line/field trial support and configs for Isolate Extensions.

content/browser/frame_host/frame_tree_browsertest.cc

Index: content/browser/frame_host/frame_tree_browsertest.cc
diff --git a/content/browser/frame_host/frame_tree_browsertest.cc b/content/browser/frame_host/frame_tree_browsertest.cc
index ee4aa82cb0530b5cc3354eefd5acc97fccf407a8..b19fcbe141458ebf88efd5dc1c93135035a34973 100644
--- a/content/browser/frame_host/frame_tree_browsertest.cc
+++ b/content/browser/frame_host/frame_tree_browsertest.cc
@@ -699,8 +699,8 @@ IN_PROC_BROWSER_TEST_F(CrossProcessFrameTreeBrowserTest,
 }
 
 // FrameTreeBrowserTest variant where we isolate http://*.is, Iceland's top
-// level domain. This is an analogue to --isolate-extensions that we use inside
-// of content_browsertests, where extensions don't exist. Iceland, like an
+// level domain. This is an analogue to isolating extensions, which we can use
+// inside content_browsertests, where extensions don't exist. Iceland, like an
 // extension process, is a special place with magical powers; we want to protect
 // it from outsiders.
 class IsolateIcelandFrameTreeBrowserTest : public ContentBrowserTest {