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 c23bdaac5bdcdb3bd924ac409b2abc37539ef948..3f7516058a0b13f797bcda127cbe40dde29b29e4 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;
@@ -153,6 +154,9 @@ public class AutocompleteController {
     public void startZeroSuggest(Profile profile, String omniboxText, String url,
             boolean focusedFromFakebox) {
         if (profile == null || TextUtils.isEmpty(url)) return;
+
+        WarmupManager.getInstance().createSpareRenderProcessHost(profile);

[Charlie Reis, 2017/06/25 23:48:27]

Worth having a comment here saying how the spare process will be used (i.e., for
either subsequent ServiceWorkers or navigations likely to result from the
upcoming search?).

[mattcary, 2017/06/26 14:45:05]

Done.

+
         mNativeAutocompleteControllerAndroid = nativeInit(profile);
         if (mNativeAutocompleteControllerAndroid != 0) {
             if (mUseCachedZeroSuggestResults) mWaitingForSuggestionsToCache = true;