Workaround for Android bug when swiped from recent tasks list.

Closes #168

https://code.google.com/p/android/issues/detail?id=53313

AndroidManifest.xml

@@ -189,6 +189,17 @@
               android:windowSoftInputMode="stateHidden"
               android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize"/>
 
+    <activity android:name=".DummyActivity"
+              android:theme="@android:style/Theme.NoDisplay"
+              android:enabled="true"
+              android:allowTaskReparenting="true"
+              android:noHistory="true"
+              android:excludeFromRecents="true"
+              android:alwaysRetainTaskState="false"
+              android:stateNotNeeded="true"
+              android:clearTaskOnLaunch="true"
+              android:finishOnTaskLaunch="true" />
+
     <service android:enabled="true" android:name=".service.ApplicationMigrationService"/>
     <service android:enabled="true" android:name=".service.KeyCachingService"/>
     <service android:enabled="true" android:name=".service.SendReceiveService"/>

src/org/thoughtcrime/securesms/DummyActivity.java

@@ -0,0 +1,16 @@
+package org.thoughtcrime.securesms;
+
+import android.app.Activity;
+import android.os.Bundle;
+
+/**
+ * Workaround for Android bug:
+ * https://code.google.com/p/android/issues/detail?id=53313
+ */
+public class DummyActivity extends Activity {
+  @Override
+  public void onCreate(Bundle bundle) {
+    super.onCreate(bundle);
+    finish();
+  }
+}

src/org/thoughtcrime/securesms/service/KeyCachingService.java

@@ -33,6 +33,7 @@ import android.util.Log;
 import android.widget.RemoteViews;
 
 import org.thoughtcrime.securesms.DatabaseUpgradeActivity;
+import org.thoughtcrime.securesms.DummyActivity;
 import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.RoutingActivity;
 import org.thoughtcrime.securesms.crypto.DecryptingQueue;
@@ -133,6 +134,17 @@ public class KeyCachingService extends Service {
     handleClearKey();
   }
 
+  /**
+   * Workaround for Android bug:
+   * https://code.google.com/p/android/issues/detail?id=53313
+   */
+  @Override
+  public void onTaskRemoved(Intent rootIntent) {
+    Intent intent = new Intent(this, DummyActivity.class);
+    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+    startActivity(intent);
+  }
+
   private void handleActivityStarted() {
     Log.w("KeyCachingService", "Incrementing activity count...");