Bug 1442250 - 4. Fix crash when child preloading fails; r=jchen

Fix a null pointer crash when we fail to preload a child process.

MozReview-Commit-ID: FIJopxOVAEj

--HG--
extra : rebase_source : 600466740c684bfadcfac0e30d5bf2fc075e4d25

mobile/android/geckoview/src/main/java/org/mozilla/gecko/process/GeckoProcessManager.java

@@ -161,8 +161,9 @@ public final class GeckoProcessManager extends IProcessManager.Stub {
     public void preload(final String... types) {
         for (final String type : types) {
             final ChildConnection connection = getConnection(type);
-            connection.bind();
-            connection.getPid();
+            if (connection.bind() != null) {
+                connection.getPid();
+            }
         }
     }