Load PackageItemInfo in background thread to prevent ANR

- Decoupled widget model from widget view, and placed the
creation to LauncherModel.
- As a result packagemanager operation, iconcache retrieval is all done inside
LauncherModel on background thread
b/21311085
b/21325319

Change-Id: I294698527db58b89f3da558090a367530c058776

src/com/android/launcher3/Utilities.java

@@ -44,6 +44,7 @@ import android.graphics.drawable.BitmapDrawable;
 import android.graphics.drawable.Drawable;
 import android.graphics.drawable.PaintDrawable;
 import android.os.Build;
+import android.os.Process;
 import android.util.Log;
 import android.util.Pair;
 import android.util.SparseArray;
@@ -57,6 +58,8 @@ import java.util.Comparator;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import junit.framework.Assert;
+
 /**
  * Various utilities shared amongst the Launcher's classes.
  */
@@ -641,4 +644,10 @@ public final class Utilities {
         return (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) &&
                 (res.getConfiguration().getLayoutDirection() == View.LAYOUT_DIRECTION_RTL);
     }
+
+    public static void assertWorkerThread() {
+        if (LauncherAppState.isDogfoodBuild()) {
+            Assert.assertTrue(LauncherModel.sWorkerThread.getThreadId() == Process.myTid());
+        }
+    }
 }