Fix issue #17492300: NavUtils.shouldUpRecreateTask returns different...

...value in L

Only do the new logic when the task is a document.

Change-Id: I4664b94a3fe86ea266c2feb4e889c14c06751a15
diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index a75fc5a..0646cce 100755
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -2856,7 +2856,8 @@
         // they need to re-create their task if this current activity is the root
         // of a document, unless simply finishing it will return them to the the
         // correct app behind.
-        if (srec.frontOfTask && srec.task != null) {
+        if (srec.frontOfTask && srec.task != null && srec.task.getBaseIntent() != null
+                && srec.task.getBaseIntent().isDocument()) {
             // Okay, this activity is at the root of its task.  What to do, what to do...
             if (srec.task.getTaskToReturnTo() != ActivityRecord.APPLICATION_ACTIVITY_TYPE) {
                 // Finishing won't return to an application, so we need to recreate.