customtabs: Initialize the spare renderer using the new WebContents method.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/WebContentsFactory.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/WebContentsFactory.java b/chrome/android/java/src/org/chromium/chrome/browser/WebContentsFactory.java
index 49ac2e299e82168abd3e496a95544f54cbdb9603..f31a7bfa3c4969f36b8ae7af1a2b52835441c839 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/WebContentsFactory.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/WebContentsFactory.java
@@ -23,9 +23,24 @@ public abstract class WebContentsFactory {
      * @return                A newly created {@link WebContents} object.
      */
     public static WebContents createWebContents(boolean incognito, boolean initiallyHidden) {
-        return nativeCreateWebContents(incognito, initiallyHidden);
+        return nativeCreateWebContents(incognito, initiallyHidden, false);
     }
 
-    private static native WebContents nativeCreateWebContents(boolean incognito,
-            boolean initiallyHidden);
+    /**
+     * A factory method to build a {@link WebContents} object.
+     *
+     * Also creates and initializes the renderer.
+     *
+     * @param incognito       Whether or not the {@link WebContents} should be built with an
+     *                        off-the-record profile or not.
+     * @param initiallyHidden Whether or not the {@link WebContents} should be initially hidden.
+     * @return                A newly created {@link WebContents} object.
+     */
+    public static WebContents createWebContentsWithWarmRenderer(
+            boolean incognito, boolean initiallyHidden) {
+        return nativeCreateWebContents(incognito, initiallyHidden, true);
+    }
+
+    private static native WebContents nativeCreateWebContents(
+            boolean incognito, boolean initiallyHidden, boolean initializeRenderer);
 }