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..860795057b949d4ab9dd1acb83bbd0e01e0b4cd6 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 +160,12 @@ public class AutocompleteController {
     public void startZeroSuggest(Profile profile, String omniboxText, String url,
             boolean focusedFromFakebox) {
         if (profile == null || TextUtils.isEmpty(url)) return;
+
+        if (!focusedFromFakebox) {

[Ted C, 2017/07/11 16:21:46]

I wonder if this should instead be NewTabPage.isNTPUrl(url) instead.  I suspect
because the renderer of the NTP is reused for the first subsequent navigation
that we don't want to do this ever from the NTP.

I think tablets will be the easiest way to test this as their NTP has both the
fakebox and the real omnibox so you could compare.

[mattcary, 2017/07/12 10:39:17]

Done.

I tested on a tablet, and using focusedFromFakebox seemed to be equivalent to
isNTPUrl. Changed anyway as the the API you suggest seems better, thanks!

+            // Proactively start up a renderer, to reduce the time to display search results,
+            // especially if a Service Worker is used.
+            WarmupManager.getInstance().createSpareRenderProcessHost(profile);
+        }
         mNativeAutocompleteControllerAndroid = nativeInit(profile);
         if (mNativeAutocompleteControllerAndroid != 0) {
             if (mUseCachedZeroSuggestResults) mWaitingForSuggestionsToCache = true;