Enable spare RenderProcessHost to be preinitialized.

chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.omnibox;
 
 import android.os.Bundle;
 import android.text.TextUtils;
 
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
+import org.chromium.chrome.browser.WarmupManager;
 import org.chromium.chrome.browser.omnibox.OmniboxSuggestion.MatchClassification;
 import org.chromium.chrome.browser.omnibox.VoiceSuggestionProvider.VoiceResult;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.content_public.browser.WebContents;
 
 import java.util.ArrayList;
 import java.util.List;
 
 /**
  * Bridge to the native AutocompleteControllerAndroid.
@@ skipping 130 matching lines @@
      *
      * @param profile The profile to use for starting the AutocompleteController.
      * @param omniboxText The text displayed in the omnibox.
      * @param url The url of the currently loaded web page.
      * @param focusedFromFakebox Whether the user entered the omnibox by tapping the fakebox on the
      *                           native NTP. This should be false on all other pages.
      */
     public void startZeroSuggest(Profile profile, String omniboxText, String url,
             boolean focusedFromFakebox) {
         if (profile == null || TextUtils.isEmpty(url)) return;
+
+        // Proactively start up a renderer, to reduce the time to display search results,
+        // especially if a Service Worker is used.
+        WarmupManager.getInstance().createSpareRenderProcessHost(profile);

[Ted C, 2017/06/30 16:16:56]

Is OmniboxPrerender fully disabled at this point?

If not, does the prerendered contents consume this or are they separate?  I'm a
bit worried that we're potentially doing too much at this point if we try to do
both and they are disjoint.

[mattcary, 2017/07/03 08:03:02]

It's 99% disabled, but that's a good point. Added logic to coordinate.

[mattcary, 2017/07/03 08:08:33]

Actually, on further reflection, the spare renderer should just get picked up by
the prerender, which is the behavior we want. I'm trying to confirm that with
traces now.

+
         mNativeAutocompleteControllerAndroid = nativeInit(profile);
         if (mNativeAutocompleteControllerAndroid != 0) {
             if (mUseCachedZeroSuggestResults) mWaitingForSuggestionsToCache = true;
             nativeOnOmniboxFocused(
                     mNativeAutocompleteControllerAndroid, omniboxText, url, focusedFromFakebox);
         }
     }
 
     /**
      * Stops generating autocomplete suggestions for the currently specified text from
@@ skipping 198 matching lines @@
      * @param query The query to be expanded into a fully qualified URL if appropriate.
      * @return The fully qualified URL or null.
      */
     public static native String nativeQualifyPartialURLQuery(String query);
 
     /**
      * Sends a zero suggest request to the server in order to pre-populate the result cache.
      */
     public static native void nativePrefetchZeroSuggestResults();
 }