customtabs: Don't create an extra child process when one is already there.

chrome/android/java/src/org/chromium/chrome/browser/init/NativeInitializationController.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.init;
 
 import android.content.Context;
 import android.content.Intent;
 import android.os.Handler;
 import android.os.Looper;
@@ skipping 54 matching lines @@
     public NativeInitializationController(Context context,
             ChromeActivityNativeDelegate activityDelegate) {
         mContext = context.getApplicationContext();
         mHandler = new Handler(Looper.getMainLooper());
         mActivityDelegate = activityDelegate;
     }
 
     /**
      * Start loading the native library in the background. This kicks off the native initialization
      * process.
+     *
+     * @param allocateChildConnection Whether a spare child connection should be allocated. Set to
+     *                                false if you know that no new renderer is needed.
      */
-    public void startBackgroundTasks() {
+    public void startBackgroundTasks(final boolean allocateChildConnection) {
         // TODO(yusufo) : Investigate using an AsyncTask for this.
         new Thread() {
             @Override
             public void run() {
                 try {
                     LibraryLoader libraryLoader =
                             LibraryLoader.get(LibraryProcessType.PROCESS_BROWSER);
                     libraryLoader.ensureInitialized(mContext.getApplicationContext());
                     // The prefetch is done after the library load for two reasons:
                     // - It is easier to know the library location after it has
                     //   been loaded.
                     // - Testing has shown that this gives the best compromise,
                     //   by avoiding performance regression on any tested
                     //   device, and providing performance improvement on
                     //   some. Doing it earlier delays UI inflation and more
                     //   generally startup on some devices, most likely by
                     //   competing for IO.
                     // For experimental results, see http://crbug.com/460438.
                     libraryLoader.asyncPrefetchLibrariesToMemory();
                 } catch (ProcessInitException e) {
                     Log.e(TAG, "Unable to load native library.", e);
                     mActivityDelegate.onStartupFailure();
                     return;
                 }
-                ChildProcessLauncher.warmUp(mContext);
+                if (allocateChildConnection) ChildProcessLauncher.warmUp(mContext);
                 ThreadUtils.runOnUiThread(new Runnable() {
                     @Override
                     public void run() {
                         onLibraryLoaded();
                     }
                 });
             }
         }.start();
     }
 
@@ skipping 149 matching lines @@
             ActivityResult activityResult;
             for (int i = 0; i < mPendingActivityResults.size(); i++) {
                 activityResult = mPendingActivityResults.get(i);
                 mActivityDelegate.onActivityResultWithNative(activityResult.requestCode,
                         activityResult.resultCode, activityResult.data);
             }
             mPendingActivityResults = null;
         }
     }
 }