Release warmed-up child process

This patch fixes a leaked service connection in the case where a tab
activity is closed after warming up the child process but before
using the child process.

Change-Id: Ia1a2346a597954b4b6a87348ab06a051652fa6c6
diff --git a/src/com/android/browser/EngineInitializer.java b/src/com/android/browser/EngineInitializer.java
index ec4753c..19b553d 100644
--- a/src/com/android/browser/EngineInitializer.java
+++ b/src/com/android/browser/EngineInitializer.java
@@ -342,6 +342,7 @@
     }
 
     public void onActivityDestroy() {
+        Engine.releaseSpareChildProcess();
         mActivityDestroyed = true;
     }