Multiple improvements to the data hub:

* Making registration finer-grained so we only listen to the data we really need.
* Moving the system listener registration to an external class (for testability and readability)
* Adding a unit test (not yet complete)
* Adding documention and cleaning up comments

Still many things TODO:
* Allow pausing of registrations
* Add pause/resume to onPause/onResume of activities
* Move sampling logic out of the hub
* Optimize data reloading when display preferences change
* (maybe) move the data hub and related classes to the "content" package

MyTracksTest/src/com/google/android/apps/mytracks/testing/TestingProviderUtilsFactory.java

@@ -0,0 +1,38 @@
+// Copyright 2010 Google Inc. All Rights Reserved.
+
+package com.google.android.apps.mytracks.testing;
+
+import com.google.android.apps.mytracks.content.MyTracksProviderUtils;
+import com.google.android.apps.mytracks.content.MyTracksProviderUtils.Factory;
+
+import android.content.Context;
+
+/**
+ * A fake factory for {@link MyTracksProviderUtils} which always returns a
+ * predefined instance.
+ *
+ * @author Rodrigo Damazio
+ */
+public class TestingProviderUtilsFactory extends Factory {
+  private MyTracksProviderUtils instance;
+
+  public TestingProviderUtilsFactory(MyTracksProviderUtils instance) {
+    this.instance = instance;
+  }
+
+  @Override
+  protected MyTracksProviderUtils newForContext(Context context) {
+    return instance;
+  }
+
+  public static Factory installWithInstance(MyTracksProviderUtils instance) {
+    Factory oldFactory = Factory.getInstance();
+    Factory factory = new TestingProviderUtilsFactory(instance);
+    MyTracksProviderUtils.Factory.overrideInstance(factory);
+    return oldFactory;
+  }
+
+  public static void restoreOldFactory(Factory factory) {
+    MyTracksProviderUtils.Factory.overrideInstance(factory);
+  }
+}