Fixing various system UI flags not getting updated properly on theme changes.

SystemUiController manages various system UI flags in priorty order and merges
all the states before applying the syste flags.
Fixing WallpaperColors when it was not handing wallpaper change properly in
some cases

Change-Id: I915442818e7888c97c81f63c8ea9f3c13053eb2c
diff --git a/src/com/android/launcher3/BaseActivity.java b/src/com/android/launcher3/BaseActivity.java
index 08cd955..2b59ede 100644
--- a/src/com/android/launcher3/BaseActivity.java
+++ b/src/com/android/launcher3/BaseActivity.java
@@ -22,11 +22,13 @@
 import android.view.View.AccessibilityDelegate;
 
 import com.android.launcher3.logging.UserEventDispatcher;
+import com.android.launcher3.util.SystemUiController;
 
 public abstract class BaseActivity extends Activity {
 
     protected DeviceProfile mDeviceProfile;
     protected UserEventDispatcher mUserEventDispatcher;
+    protected SystemUiController mSystemUiController;
 
     public DeviceProfile getDeviceProfile() {
         return mDeviceProfile;
@@ -54,4 +56,11 @@
         }
         return ((BaseActivity) ((ContextWrapper) context).getBaseContext());
     }
+
+    public SystemUiController getSystemUiController() {
+        if (mSystemUiController == null) {
+            mSystemUiController = new SystemUiController(getWindow());
+        }
+        return mSystemUiController;
+    }
 }