Enable spare RenderProcessHost to be preinitialized.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java b/chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java
index 12ecd35ff03162d45aaf18738d8d58d586febec6..e5d294280733f2a87997285830c603b436746dc3 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/omnibox/AutocompleteController.java
@@ -9,6 +9,7 @@ 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;
@@ -159,6 +160,11 @@ public class AutocompleteController {
     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;