Prevent accounts page directly opening in screen pinning mode

In Settings there is no auth mechanism to prevent accounts page being
opened in screen pinning mode. This CL makes it so that when users are
trying to navigate to any pages in Settings from other apps in screen
pinning mode, Settings app will directly close its page.

Bug: 137015265
Bug: 135604684
Test: manual
Change-Id: If26eda408a9ef6fa03ad82e5bee51bb7185950d6
Merged-In: If26eda408a9ef6fa03ad82e5bee51bb7185950d6
(cherry picked from commit f3242dab35)

src/com/android/settings/SettingsActivity.java

@@ -277,6 +277,12 @@ public class SettingsActivity extends SettingsDrawerActivity
     @Override
     protected void onCreate(Bundle savedState) {
         super.onCreate(savedState);
+
+        if (isLockTaskModePinned() && !isSettingsRunOnTop()) {
+            Log.w(LOG_TAG, "Devices lock task mode pinned.");
+            finish();
+        }
+
         long startTime = System.currentTimeMillis();
 
         final FeatureFactory factory = FeatureFactory.getFactory(this);
@@ -939,4 +945,19 @@ public class SettingsActivity extends SettingsDrawerActivity
 
         return bitmap;
     }
+
+
+    private boolean isLockTaskModePinned() {
+        final ActivityManager activityManager =
+            getApplicationContext().getSystemService(ActivityManager.class);
+        return activityManager.getLockTaskModeState() == ActivityManager.LOCK_TASK_MODE_PINNED;
+    }
+
+    private boolean isSettingsRunOnTop() {
+        final ActivityManager activityManager =
+            getApplicationContext().getSystemService(ActivityManager.class);
+        final String taskPkgName = activityManager.getRunningTasks(1 /* maxNum */)
+            .get(0 /* index */).baseActivity.getPackageName();
+        return TextUtils.equals(getPackageName(), taskPkgName);
+    }
 }