Update web shell app to not load dev.chromium.org on launch.

ios/web/shell/test/earl_grey/shell_earl_grey.mm

Index: ios/web/shell/test/earl_grey/shell_earl_grey.mm
diff --git a/ios/web/shell/test/earl_grey/shell_earl_grey.mm b/ios/web/shell/test/earl_grey/shell_earl_grey.mm
index 17c55d91dc39ed5f36ad86b2149535e99b0e56cc..bdf8f1b47face21f3577251265b48677eb79864c 100644
--- a/ios/web/shell/test/earl_grey/shell_earl_grey.mm
+++ b/ios/web/shell/test/earl_grey/shell_earl_grey.mm
@@ -34,6 +34,10 @@
   web::WebState* webState = web::shell_test_util::GetCurrentWebState();
   if (webState->ContentIsHTML())
     web::WaitUntilWindowIdInjected(webState);
+
+  // Ensure any UI elements handled by EarlGrey become idle for any subsequent
+  // EarlGrey steps.
+  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
 }
 
 @end