Add code to prefetch a DNS resolution for a given URL.

chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java b/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
index a0b751553e38a4e22ce2639a2539a909f8fbdf56..702ebedd9a0a4780208e253a6a5351d06894d910 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
@@ -5,6 +5,7 @@
 package org.chromium.chrome.browser;
 
 import android.content.Context;
+import android.os.AsyncTask;
 import android.view.ContextThemeWrapper;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -12,10 +13,16 @@ import android.view.ViewGroup;
 import android.widget.FrameLayout;
 
 import org.chromium.base.ThreadUtils;
+import org.chromium.chrome.browser.net.spdyproxy.DataReductionProxySettings;
 import org.chromium.chrome.browser.prerender.ExternalPrerenderHandler;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.content_public.browser.WebContents;
 
+import java.net.InetAddress;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.UnknownHostException;
+
 /**
  * This class is a singleton that holds utilities for warming up Chrome and prerendering urls
  * without creating the Activity.
@@ -155,4 +162,39 @@ public final class WarmupManager {
         mMainView = null;
         return mainView;
     }
+
+    /**
+     * Launches a background DNS query for a given URL.
+     *
+     * @param urlString URL from which the domain to query is extracted.
+     */
+    private static void prefetchDnsForUrlInBackground(String urlString) {
+        new AsyncTask<String, Void, Void>() {
+            @Override
+            protected Void doInBackground(String... params) {
+                try {
+                    URL url = new URL(params[0]);
+                    InetAddress.getByName(url.getHost());
+                } catch (MalformedURLException e) {
+                    // We don't do anything with the result of the resolution,
+                    // it is only here to warm the DNS cache. So ignoring all
+                    // exceptions is fine.
+                } catch (UnknownHostException e) {
+                    // Idem
+                }
+                return null;
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, urlString);
+    }
+
+    /** Launches a background DNS query for a given URL if the data reduction proxy is not in use.
+     *
+     * @param context The Application context.
+     * @param url URL from which the domain to query is extracted.
+     */
+    public static void maybePrefetchDnsForUrlInBackground(Context context, String url) {
+        if (!DataReductionProxySettings.isEnabledBeforeNativeLoad(context)) {
+            prefetchDnsForUrlInBackground(url);
+        }
+    }
 }