Lazy loading LauncherAppState

Separating InvarantDeviceProfile out of LauncherAppState and creating
LauncherAppState only when it is actually used

Change-Id: I2ee55f53cae01f11203f94675bb5f70c65ad2b9d

src/com/android/launcher3/util/MainThreadInitializedObject.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.launcher3.util;
+
+import android.content.Context;
+import android.os.Looper;
+
+import com.android.launcher3.MainThreadExecutor;
+
+import java.util.concurrent.ExecutionException;
+
+/**
+ * Utility class for defining singletons which are initiated on main thread.
+ */
+public class MainThreadInitializedObject<T> {
+
+    private final ObjectProvider<T> mProvider;
+    private T mValue;
+
+    public MainThreadInitializedObject(ObjectProvider<T> provider) {
+        mProvider = provider;
+    }
+
+    public T get(Context context) {
+        if (mValue == null) {
+            if (Looper.myLooper() == Looper.getMainLooper()) {
+                mValue = mProvider.get(context.getApplicationContext());
+            } else {
+                try {
+                    return new MainThreadExecutor().submit(() -> get(context)).get();
+                } catch (InterruptedException|ExecutionException e) {
+                    throw new RuntimeException(e);
+                }
+            }
+        }
+        return mValue;
+    }
+
+    public T getNoCreate() {
+        return mValue;
+    }
+
+    public interface ObjectProvider<T> {
+
+        T get(Context context);
+    }
+}