Don't block activity starts in permissive mode.

When activity starts have been enabled via developer options we
shouldn't block them. But we still want to show a toast to warn that
the start would have been blocked.

Scenarios where we were blocking when we shouldn't:
- Creating a new task from a background receiver (here the activity is
  created but not brought to the front).
- Starting an activity while app switching protection is in force.
- Various cases when starting an activity in a new task or a task that
  doesn't already have one of our activities in it.

Bug: 132919170
Bug: 132919170
Test: manual
Test: atest BackgroundActivityLaunchTest
Test: atest RootWindowContainerTests
Test: atest WmTests:ActivityStarterTests
Test: atest CtsWindowManagerDeviceTestCases:ActivityStarterTests
Test: atest CtsAppTestCases:.ServiceTest
Change-Id: I32d75d04ea93cb4883e93bbe74468755a708ca24

services/core/java/com/android/server/wm/ActivityStarter.java

@@ -161,7 +161,7 @@ class ActivityStarter {
     private ActivityOptions mOptions;
 
     // If it is true, background activity can only be started in an existing task that contains
-    // an activity with same uid.
+    // an activity with same uid, or if activity starts are enabled in developer options.
     private boolean mRestrictedBgActivity;
 
     private int mLaunchMode;
@@ -921,7 +921,7 @@ class ActivityStarter {
                 || stack.getResumedActivity().info.applicationInfo.uid != realCallingUid)) {
             if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid,
                     realCallingPid, realCallingUid, "Activity start")) {
-                if (!restrictedBgActivity) {
+                if (!(restrictedBgActivity && handleBackgroundActivityAbort(r))) {
                     mController.addPendingActivityLaunch(new PendingActivityLaunch(r,
                             sourceRecord, startFlags, stack, callerApp));
                 }
@@ -1916,7 +1916,7 @@ class ActivityStarter {
 
         mNoAnimation = (mLaunchFlags & FLAG_ACTIVITY_NO_ANIMATION) != 0;
 
-        if (restrictedBgActivity) {
+        if (mRestrictedBgActivity && !mService.isBackgroundActivityStartsEnabled()) {
             mAvoidMoveToFront = true;
             mDoResume = false;
         }
@@ -2380,7 +2380,6 @@ class ActivityStarter {
             if (handleBackgroundActivityAbort(mStartActivity)) {
                 return START_ABORTED;
             }
-            return START_ABORTED;
         }
         // We only want to allow changing stack in two cases:
         // 1. If the target task is not the top one. Otherwise we would move the launching task to
@@ -2553,17 +2552,15 @@ class ActivityStarter {
             if (handleBackgroundActivityAbort(mStartActivity)) {
                 return START_ABORTED;
             }
-            return START_ABORTED;
         }
         final TaskRecord task = (prev != null)
                 ? prev.getTaskRecord() : mTargetStack.createTaskRecord(
                 mSupervisor.getNextTaskIdForUserLocked(mStartActivity.mUserId), mStartActivity.info,
                 mIntent, null, null, true, mStartActivity, mSourceRecord, mOptions);
-        if (mRestrictedBgActivity && !task.containsAppUid(mCallingUid)) {
+        if (mRestrictedBgActivity && prev != null && !task.containsAppUid(mCallingUid)) {
             if (handleBackgroundActivityAbort(mStartActivity)) {
                 return START_ABORTED;
             }
-            return START_ABORTED;
         }
         addOrReparentStartingActivity(task, "setTaskToCurrentTopOrCreateNewTask");
         mTargetStack.positionChildWindowContainerAtTop(task);