Dismiss system windows when screen savers start.

Also add a couple more flags to the intent:
 - NO_HISTORY (finish activity on suspend)
 - FLAG_FROM_BACKGROUND

Bug: 5578434
Change-Id: I97b965175a27760b819dc29ddb57865c5f4754d6

Author: dsandler

packages/SystemUI/src/com/android/systemui/DreamsDockLauncher.java

@@ -30,12 +30,17 @@ private static void launchDream(Context context) {
                     com.android.internal.R.string.config_defaultDreamComponent);
             }
             if (component != null) {
+                // dismiss the notification shade, recents, etc.
+                context.sendBroadcast(new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS));
+
                 ComponentName cn = ComponentName.unflattenFromString(component);
                 Intent zzz = new Intent(Intent.ACTION_MAIN)
                     .setComponent(cn)
                     .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
-                        | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS
-                        | Intent.FLAG_ACTIVITY_NO_USER_ACTION
+                            | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS
+                            | Intent.FLAG_ACTIVITY_NO_USER_ACTION
+                            | Intent.FLAG_FROM_BACKGROUND
+                            | Intent.FLAG_ACTIVITY_NO_HISTORY
                         );
                 Slog.v(TAG, "Starting screen saver on dock event: " + component);
                 context.startActivity(zzz);

policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

@@ -3475,12 +3475,17 @@ public void run() {
                     component = mContext.getResources().getString(R.string.config_defaultDreamComponent);
                 }
                 if (component != null) {
+                    // dismiss the notification shade, recents, etc.
+                    mContext.sendBroadcast(new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS));
+
                     ComponentName cn = ComponentName.unflattenFromString(component);
                     Intent intent = new Intent(Intent.ACTION_MAIN)
                         .setComponent(cn)
                         .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
                             | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS
                             | Intent.FLAG_ACTIVITY_NO_USER_ACTION
+                            | Intent.FLAG_FROM_BACKGROUND
+                            | Intent.FLAG_ACTIVITY_NO_HISTORY
                             );
                     mContext.startActivity(intent);
                 } else {