Only commit cookie changes in prerenders after a prerender is shown

chrome/android/javatests/src/org/chromium/chrome/browser/prerender/ExternalPrerenderRequestTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/prerender/ExternalPrerenderRequestTest.java
===================================================================
--- chrome/android/javatests/src/org/chromium/chrome/browser/prerender/ExternalPrerenderRequestTest.java	(revision 269838)
+++ chrome/android/javatests/src/org/chromium/chrome/browser/prerender/ExternalPrerenderRequestTest.java	(working copy)
@@ -21,11 +21,14 @@
  * Tests for adding and removing prerenders using the {@link ExternalPrerenderHandler}
  */
 public class ExternalPrerenderRequestTest extends ChromeShellTestBase {
+    private static final String HOMEPAGE_URL =
+            TestHttpServerClient.getUrl("chrome/test/data/android/prerender/homepage.html");
     private static final String GOOGLE_URL =
             TestHttpServerClient.getUrl("chrome/test/data/android/prerender/google.html");
     private static final String YOUTUBE_URL =
             TestHttpServerClient.getUrl("chrome/test/data/android/prerender/youtube.html");
     private static final int PRERENDER_DELAY_MS = 500;
+    private static final int CHECK_COOKIE_STORE_FREQUENCY_MS = 200;
 
     private ExternalPrerenderHandler mHandler;
     private Profile mProfile;
@@ -34,7 +37,8 @@
     public void setUp() throws Exception {
         super.setUp();
         clearAppData();
-        launchChromeShellWithBlankPage();
+        // Launch with a non-blank homepage, to trigger cookie store loading.
+        launchChromeShellWithUrl(HOMEPAGE_URL);
         assertTrue(waitForActiveShellToBeDoneLoading());
         mHandler = new ExternalPrerenderHandler();
         final Callable<Profile> profileCallable = new Callable<Profile>() {
@@ -44,6 +48,8 @@
             }
         };
         mProfile = ThreadUtils.runOnUiThreadBlocking(profileCallable);
+        while (!ExternalPrerenderHandler.hasCookieStoreLoaded(mProfile))
+            Thread.sleep(CHECK_COOKIE_STORE_FREQUENCY_MS);
     }
 
     @MediumTest