Docsui-level work for implementing Eject on Roots list.

1. Added Eject Icon for Roots that support eject
2. Added Context Menu for RootsFragment (Settings and Eject)

Bug: 29584653
Change-Id: I97f582de05763e3f0327bc0d2dc6d4e2222e047c
(cherry picked from commit d96661f8b0f613b40f2bdfc178bbe06022b5f76c)

1 files changed, 79 insertions, 0 deletions

diff --git a/packages/DocumentsUI/src/com/android/documentsui/CheckedTask.java b/packages/DocumentsUI/src/com/android/documentsui/CheckedTask.java
new file mode 100644
index 000000000000..ae159021e76a
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/CheckedTask.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2016 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.documentsui;
+
+import android.os.AsyncTask;
+
+/**
+ * An {@link AsyncTask} that guards work with checks that a paired {@link Check}
+ * has not yet given signals to stop progress.
+ *
+ * <p>Use this type of task for greater safety when executing tasks that might complete
+ * after the owner of the task has explicitly given a signal to stop progress.
+ *
+ * <p>Also useful as tasks can be static, limiting scope, but still have access to
+ * signal from the owning class.
+ *
+ * @template Input input type
+ * @template Output output type
+ */
+abstract class CheckedTask<Input, Output>
+        extends AsyncTask<Input, Void, Output> {
+
+    private Check mCheck ;
+
+    public CheckedTask(Check check) {
+        mCheck = check;
+    }
+
+    /** Called prior to run being executed. Analogous to {@link AsyncTask#onPreExecute} */
+    void prepare() {}
+
+    /** Analogous to {@link AsyncTask#doInBackground} */
+    abstract Output run(Input... input);
+
+    /** Analogous to {@link AsyncTask#onPostExecute} */
+    abstract void finish(Output output);
+
+    @Override
+    final protected void onPreExecute() {
+        if (mCheck.stop()) {
+            return;
+        }
+        prepare();
+    }
+
+    @Override
+    final protected Output doInBackground(Input... input) {
+        if (mCheck.stop()) {
+            return null;
+        }
+        return run(input);
+    }
+
+    @Override
+    final protected void onPostExecute(Output result) {
+        if (mCheck.stop()) {
+            return;
+        }
+        finish(result);
+    }
+
+    interface Check {
+        boolean stop();
+    }
+}