Implement touch events for site-isolation.

chrome/browser/apps/guest_view/web_view_browsertest.cc

Index: chrome/browser/apps/guest_view/web_view_browsertest.cc
diff --git a/chrome/browser/apps/guest_view/web_view_browsertest.cc b/chrome/browser/apps/guest_view/web_view_browsertest.cc
index 54645635bdece3348d4b6cb0b61e17c47d225d96..b04a839558d7f5a80ab435a55b844b8b7c7ef583 100644
--- a/chrome/browser/apps/guest_view/web_view_browsertest.cc
+++ b/chrome/browser/apps/guest_view/web_view_browsertest.cc
@@ -891,8 +891,10 @@ IN_PROC_BROWSER_TEST_P(WebViewTest, ReloadEmbedder) {
 }
 
 IN_PROC_BROWSER_TEST_P(WebViewTest, AcceptTouchEvents) {
-  // TODO(lfg): Fix touch events for OOPIF-based webview.
-  // https://crbug.com/581892
+  // This test only makes sense for non-OOPIF WebView, since with
+  // UseCrossProcessFramesForGuests() events are routed directly to the
+  // guest, so the embedder does not need to know about the installation of
+  // touch handlers.
   if (content::BrowserPluginGuestMode::UseCrossProcessFramesForGuests())
     return;