Enable spare RenderProcessHost to be preinitialized.

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 7c6ccb38bc737891664f5ace3b09ebee4922aeba..ab0bfccabc8f7b46487b628b59e457c72000ff1f 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/WarmupManager.java
@@ -248,6 +248,25 @@ public final class WarmupManager {
         }
     }
 
+    /**
+     * Warms up a spare, empty RenderProcessHost that may be used for subsequent navigations.
+     *
+     * The spare RenderProcessHost will be used automatically in subsequent navigations.
+     * There is nothing further the WarmupManager needs to do to enable that use.
+     *
+     * This uses a different mechanism than createSpareWebContents, below, and is subject
+     * to fewer restrictions.
+     *
+     * This must be called from the UI thread.
+     */
+    public void createSpareRenderProcessHost(Profile profile) {
+        ThreadUtils.assertOnUiThread();
+        // Spare WebContents should not be used with spare RenderProcessHosts, but if one
+        // has been created, destroy it in order not to consume too many processes.
+        destroySpareWebContents();
+        nativeWarmupSpareRenderer(profile);
+    }
+
     /**
      * Creates and initializes a spare WebContents, to be used in a subsequent navigation.
      *
@@ -314,4 +333,5 @@ public final class WarmupManager {
     }
 
     private static native void nativePreconnectUrlAndSubresources(Profile profile, String url);
+    private static native void nativeWarmupSpareRenderer(Profile profile);
 }