Fix minor issues discovered with Multi-Display tests

- NPE when launching activity on secondary display
and there is a docked stack on primary.
- Activities not finished correctly on secondary display
when it is removed.

Change-Id: If527211e8192088790d32b9673b960535e27033f
Test: See ActivityManagerDisplayTests.
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 1cbb52f..539ac16 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -3564,7 +3564,10 @@
             if (activityDisplay != null) {
                 ArrayList<ActivityStack> stacks = activityDisplay.mStacks;
                 for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
-                    stacks.get(stackNdx).mActivityContainer.removeLocked();
+                    final ActivityStack stack = stacks.get(stackNdx);
+                    // TODO: Implement proper stack removal and ability to choose the behavior -
+                    // remove stack completely or move it to other display.
+                    moveStackToDisplayLocked(stack.mStackId, DEFAULT_DISPLAY);
                 }
                 mActivityDisplays.remove(displayId);
             }
@@ -4215,7 +4218,10 @@
             }
         }
 
-        /** Remove the stack completely. */
+        /**
+         * Remove the stack completely. Must be called only when there are no tasks left in it,
+         * as this method does not finish running activities.
+         */
         void removeLocked() {
             if (DEBUG_STACK) Slog.d(TAG_STACK, "removeLocked: " + this + " from display="
                     + mActivityDisplay + " Callers=" + Debug.getCallers(2));
diff --git a/services/core/java/com/android/server/am/ActivityStarter.java b/services/core/java/com/android/server/am/ActivityStarter.java
index c96e74f..709c3d0 100644
--- a/services/core/java/com/android/server/am/ActivityStarter.java
+++ b/services/core/java/com/android/server/am/ActivityStarter.java
@@ -257,11 +257,7 @@
 
         if (err == ActivityManager.START_SUCCESS) {
             Slog.i(TAG, "START u" + userId + " {" + intent.toShortString(true, true, true, false)
-                    + "} from uid " + callingUid
-                    + " on display " + (container == null ? (mSupervisor.mFocusedStack == null ?
-                    Display.DEFAULT_DISPLAY : mSupervisor.mFocusedStack.mDisplayId) :
-                    (container.mActivityDisplay == null ? Display.DEFAULT_DISPLAY :
-                            container.mActivityDisplay.mDisplayId)));
+                    + "} from uid " + callingUid);
         }
 
         ActivityRecord sourceRecord = null;
diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index c8e35eb..e73acde 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -727,7 +727,8 @@
             win.getTouchableRegion(mTmpRegion);
             mTouchExcludeRegion.op(mTmpRegion, Region.Op.UNION);
         }
-        if (getDockedStackLocked() != null) {
+        // TODO(multi-display): Support docked stacks on secondary displays.
+        if (mDisplayId == DEFAULT_DISPLAY && getDockedStackLocked() != null) {
             mDividerControllerLocked.getTouchRegion(mTmpRect);
             mTmpRegion.set(mTmpRect);
             mTouchExcludeRegion.op(mTmpRegion, Op.UNION);