Add Early DNS prefetching to ChromeShell.

The actual code was added in https://codereview.chromium.org/909893003
and enabled downstream, but not in ChromeShell.

BUG=458216

Review URL: https://codereview.chromium.org/1029583006

Cr-Commit-Position: refs/heads/master@{#327251}

chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellActivity.java

@@ -32,6 +32,7 @@ import org.chromium.base.library_loader.ProcessInitException;
 import org.chromium.chrome.browser.DevToolsServer;
 import org.chromium.chrome.browser.FileProviderHelper;
 import org.chromium.chrome.browser.Tab;
+import org.chromium.chrome.browser.WarmupManager;
 import org.chromium.chrome.browser.WebsiteSettingsPopup;
 import org.chromium.chrome.browser.appmenu.AppMenuHandler;
 import org.chromium.chrome.browser.appmenu.AppMenuPropertiesDelegate;
@@ -124,6 +125,11 @@ public class ChromeShellActivity extends AppCompatActivity implements AppMenuPro
 
         DeviceUtils.addDeviceSpecificUserAgentSwitch(this);
 
+        String url = getUrlFromIntent(getIntent());
+        if (url != null) {
+            WarmupManager.getInstance().maybePrefetchDnsForUrlInBackground(this, url);
+        }
+
         BrowserStartupController.StartupCallback callback =
                 new BrowserStartupController.StartupCallback() {
                     @Override