[ios][eg2] Fix flakiness in testRequestMobileSitePropagatesToNextNavigations

This increases the timeout used when waiting for a web state after switching
to desktop or mobile mode from 10 seconds to 15 seconds.

The previous value (10 seconds) had been chosen since that was sufficient to
fix flake locally when this test was converted to EG2.

Bug: 1037663
Change-Id: I37c56cb30ab1158b36c95d88a53b2e45ea009cbe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1988488Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Ali Juma <ajuma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728594}

ios/chrome/browser/ui/popup_menu/request_desktop_mobile_site_egtest.mm

@@ -32,7 +32,7 @@ const char kDesktopSiteLabel[] = "Desktop";
 
 // Custom timeout used when waiting for a web state after requesting desktop
 // or mobile mode.
-const NSTimeInterval kWaitForUserAgentChangeTimeout = 10.0;
+const NSTimeInterval kWaitForUserAgentChangeTimeout = 15.0;
 
 // Select the button to request desktop site by scrolling the collection.
 // 200 is a reasonable scroll displacement that works for all UI elements, while
@@ -169,15 +169,7 @@ class UserAgentResponseProvider : public web::DataResponseProvider {
 
 // Tests that requesting mobile site of a page works and the user agent
 // propagates to the next navigations in the same tab.
-// TODO(crbug.com/1037663): Enable for EG2.
-#if defined(CHROME_EARL_GREY_2)
-#define MAYBE_testRequestMobileSitePropagatesToNextNavigations \
-  FLAKY_testRequestMobileSitePropagatesToNextNavigations
-#else
-#define MAYBE_testRequestMobileSitePropagatesToNextNavigations \
-  testRequestMobileSitePropagatesToNextNavigations
-#endif
-- (void)MAYBE_testRequestMobileSitePropagatesToNextNavigations {
+- (void)testRequestMobileSitePropagatesToNextNavigations {
   std::unique_ptr<web::DataResponseProvider> provider(
       new UserAgentResponseProvider());
   web::test::SetUpHttpServer(std::move(provider));