Make sure mFocusedStack is never the home stack.

There were circumstances where mFocusedStack could be assigned the
home stack. If this were ever to occur then all subsequent tasks would
be put on the home stack. This fix ensures that there is no way that
mFocusedStack will ever be assigned to the home task.

Fixes bug 11271189.

Change-Id: I7ddd9b6bcbf2787cbe2f44b461ad057ae2241f00
diff --git a/services/java/com/android/server/am/ActivityStackSupervisor.java b/services/java/com/android/server/am/ActivityStackSupervisor.java
index 523015d..14312b6 100644
--- a/services/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/java/com/android/server/am/ActivityStackSupervisor.java
@@ -1254,15 +1254,16 @@
         final TaskRecord task = r.task;
         if (r.isApplicationActivity() || (task != null && task.isApplicationTask())) {
             if (task != null) {
-                if (mFocusedStack != task.stack) {
+                final ActivityStack taskStack = task.stack;
+                if (mFocusedStack != taskStack) {
                     if (DEBUG_FOCUS || DEBUG_STACK) Slog.d(TAG,
                             "adjustStackFocus: Setting focused stack to r=" + r + " task=" + task);
-                    mFocusedStack = task.stack;
+                    mFocusedStack = taskStack.isHomeStack() ? null : taskStack;
                 } else {
                     if (DEBUG_FOCUS || DEBUG_STACK) Slog.d(TAG,
                         "adjustStackFocus: Focused stack already=" + mFocusedStack);
                 }
-                return mFocusedStack;
+                return taskStack;
             }
 
             if (mFocusedStack != null) {
@@ -1282,8 +1283,8 @@
             }
 
             // Time to create the first app stack for this user.
-            int stackId = mService.createStack(-1, HOME_STACK_ID,
-                StackBox.TASK_STACK_GOES_OVER, 1.0f);
+            int stackId =
+                    mService.createStack(-1, HOME_STACK_ID, StackBox.TASK_STACK_GOES_OVER, 1.0f);
             if (DEBUG_FOCUS || DEBUG_STACK) Slog.d(TAG, "adjustStackFocus: New stack r=" + r +
                     " stackId=" + stackId);
             mFocusedStack = getStack(stackId);
@@ -1308,7 +1309,8 @@
             if (DEBUG_FOCUS || DEBUG_STACK) Slog.d(TAG,
                     "setFocusedStack: Setting focused stack to r=" + r + " task=" + r.task +
                     " Callers=" + Debug.getCallers(3));
-            mFocusedStack = r.task.stack;
+            final ActivityStack taskStack = r.task.stack;
+            mFocusedStack = taskStack.isHomeStack() ? null : taskStack;
             if (mStackState != STACK_STATE_HOME_IN_BACK) {
                 if (DEBUG_STACK) Slog.d(TAG, "setFocusedStack: mStackState old=" +
                         stackStateToString(mStackState) + " new=" +
@@ -2367,12 +2369,13 @@
     }
 
     public void dump(PrintWriter pw, String prefix) {
-        pw.print(prefix); pw.print("mDismissKeyguardOnNextActivity:");
+        pw.print(prefix); pw.print("mDismissKeyguardOnNextActivity=");
                 pw.println(mDismissKeyguardOnNextActivity);
-        pw.print(prefix); pw.print("mStackState="); pw.println(stackStateToString(mStackState));
-        pw.print(prefix); pw.println("mSleepTimeout: " + mSleepTimeout);
-        pw.print(prefix); pw.println("mCurTaskId: " + mCurTaskId);
-        pw.print(prefix); pw.println("mUserStackInFront: " + mUserStackInFront);
+        pw.print(prefix); pw.print("mFocusedStack=" + mFocusedStack);
+                pw.print(" mStackState="); pw.println(stackStateToString(mStackState));
+        pw.print(prefix); pw.println("mSleepTimeout=" + mSleepTimeout);
+        pw.print(prefix); pw.println("mCurTaskId=" + mCurTaskId);
+        pw.print(prefix); pw.println("mUserStackInFront=" + mUserStackInFront);
     }
 
     ArrayList<ActivityRecord> getDumpActivitiesLocked(String name) {