Tweak Demo app code to facilitate overriding Application methods and change the used DataSourceFactory.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131288634

demo/src/main/AndroidManifest.xml

@@ -29,7 +29,8 @@
       android:label="@string/application_name"
       android:icon="@drawable/ic_launcher"
       android:largeHeap="true"
-      android:allowBackup="false">
+      android:allowBackup="false"
+      android:name=".DemoApplication">
 
     <activity android:name="com.google.android.exoplayer2.demo.SampleChooserActivity"
         android:configChanges="keyboardHidden"

demo/src/main/java/com/google/android/exoplayer2/demo/DemoApplication.java

@@ -0,0 +1,24 @@
+/*
+ * 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.google.android.exoplayer2.demo;
+
+import android.app.Application;
+
+/**
+ * Placeholder application to facilitate overriding Application methods for debugging and testing.
+ */
+public class DemoApplication extends Application {
+}

demo/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -69,6 +69,7 @@ import com.google.android.exoplayer2.ui.KeyCompatibleMediaController;
 import com.google.android.exoplayer2.ui.MediaControllerPrevNextClickListener;
 import com.google.android.exoplayer2.ui.PlayerControl;
 import com.google.android.exoplayer2.ui.SubtitleView;
+import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.DefaultBandwidthMeter;
 import com.google.android.exoplayer2.upstream.DefaultDataSourceFactory;
 import com.google.android.exoplayer2.upstream.DefaultHttpDataSource;
@@ -118,7 +119,7 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
   private Button retryButton;
 
   private String userAgent;
-  private DefaultDataSourceFactory mediaDataSourceFactory;
+  private DataSource.Factory mediaDataSourceFactory;
   private SimpleExoPlayer player;
   private MappingTrackSelector trackSelector;
   private TrackSelectionHelper trackSelectionHelper;
@@ -135,7 +136,7 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
   public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     userAgent = Util.getUserAgent(this, "ExoPlayerDemo");
-    mediaDataSourceFactory = new DefaultDataSourceFactory(this, userAgent, BANDWIDTH_METER);
+    mediaDataSourceFactory = buildMediaDataSourceFactory();
     mainHandler = new Handler();
     if (CookieHandler.getDefault() != DEFAULT_COOKIE_MANAGER) {
       CookieHandler.setDefault(DEFAULT_COOKIE_MANAGER);
@@ -338,10 +339,10 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
         : uri.getLastPathSegment());
     switch (type) {
       case Util.TYPE_SS:
-        return new SsMediaSource(uri, new DefaultDataSourceFactory(this, userAgent),
+        return new SsMediaSource(uri, buildManifestDataSourceFactory(),
             new DefaultSsChunkSource.Factory(mediaDataSourceFactory), mainHandler, eventLogger);
       case Util.TYPE_DASH:
-        return new DashMediaSource(uri, new DefaultDataSourceFactory(this, userAgent),
+        return new DashMediaSource(uri, buildManifestDataSourceFactory(),
             new DefaultDashChunkSource.Factory(mediaDataSourceFactory), mainHandler, eventLogger);
       case Util.TYPE_HLS:
         return new HlsMediaSource(uri, mediaDataSourceFactory, mainHandler, eventLogger);
@@ -392,6 +393,16 @@ public class PlayerActivity extends Activity implements OnKeyListener, OnTouchLi
     }
   }
 
+  /** Build a DataSource factory for manifest data, that does not affect the bandwidth estimate. */
+  private DataSource.Factory buildManifestDataSourceFactory() {
+    return new DefaultDataSourceFactory(this, userAgent);
+  }
+
+  /** Build a DataSource factory for media data, that does affect the bandwidth estimate. */
+  private DataSource.Factory buildMediaDataSourceFactory() {
+    return new DefaultDataSourceFactory(this, userAgent, BANDWIDTH_METER);
+  }
+
   // ExoPlayer.EventListener implementation
 
   @Override