Added the icon displayed on no account in search bar

Mofidied the search_bar layout and added this icon in the right side of the search_bar.
Added the hasAccount api in AvatarViewMixin and display this icon when there is no any account in device.
Added the test case of the AvatarViewMixin.

Bug: 117509285
Test: robotest
Change-Id: I6ceaa457af4fb20acd0211ca840df5b530c47e0f

src/com/android/settings/accounts/AvatarViewMixin.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.settings.accounts;
+
+import android.accounts.Account;
+import android.content.Context;
+import android.widget.ImageView;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
+
+import com.android.settings.R;
+import com.android.settings.homepage.SettingsHomepageActivity;
+import com.android.settings.overlay.FeatureFactory;
+
+/**
+ * Avatar related work to the onStart method of registered observable classes
+ * in {@link SettingsHomepageActivity}.
+ */
+public class AvatarViewMixin implements LifecycleObserver {
+    private Context mContext;
+    private ImageView mAvatarView;
+
+    public AvatarViewMixin(Context context, ImageView avatarView) {
+        mContext = context.getApplicationContext();
+        mAvatarView = avatarView;
+    }
+
+    @OnLifecycleEvent(Lifecycle.Event.ON_START)
+    public void onStart() {
+        if (hasAccount()) {
+            //TODO(b/117509285): To migrate account icon on search bar
+        } else {
+            mAvatarView.setImageResource(R.drawable.ic_account_circle_24dp);
+        }
+    }
+
+    @VisibleForTesting
+    boolean hasAccount() {
+        final Account accounts[] = FeatureFactory.getFactory(
+                mContext).getAccountFeatureProvider().getAccounts(mContext);
+        return (accounts != null) && (accounts.length > 0);
+    }
+}