Instead of guessing, compute center point of Guest View for test.

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 84d41e652f5cfb48b1dfe23b3af5658a2605778a..a134257cd50070390bb7e2fe286d6f8de3ba57e8 100644
--- a/chrome/browser/apps/guest_view/web_view_browsertest.cc
+++ b/chrome/browser/apps/guest_view/web_view_browsertest.cc
@@ -2520,11 +2520,17 @@ IN_PROC_BROWSER_TEST_F(WebViewFocusTest, TouchFocusesEmbedder) {
   EXPECT_TRUE(other_focusable_view->HasFocus());
   EXPECT_FALSE(aura_webview->HasFocus());
 
+  // Compute location of guest within embedder so we can more accurately
+  // target our touch event.
+  gfx::Rect guest_rect = GetGuestWebContents()->GetContainerBounds();
+  gfx::Point embedder_origin =
+      GetEmbedderWebContents()->GetContainerBounds().origin();
+  guest_rect.Offset(-embedder_origin.x(), -embedder_origin.y());
+
   // Generate and send synthetic touch event.
-  // TODO(wjmaclean): This is fragile ... if anyone alters the location/size
-  // of the webview in accept_touch_events then this may miss its target.
   FocusWaiter waiter(aura_webview);
-  content::SimulateTouchPressAt(GetEmbedderWebContents(), gfx::Point(10, 10));
+  content::SimulateTouchPressAt(GetEmbedderWebContents(),
+                                guest_rect.CenterPoint());
 
   // Wait for the TouchStart to propagate and restore focus. Test times out
   // on failure.