diff -r 000000000000 -r 6474c204b198 mobile/android/base/fxa/login/FxAccountLoginStateMachine.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/fxa/login/FxAccountLoginStateMachine.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,84 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.fxa.login;
+
+import java.security.NoSuchAlgorithmException;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.mozilla.gecko.background.fxa.FxAccountClient;
+import org.mozilla.gecko.browserid.BrowserIDKeyPair;
+import org.mozilla.gecko.fxa.login.FxAccountLoginTransition.Transition;
+import org.mozilla.gecko.fxa.login.State.StateLabel;
+
+public class FxAccountLoginStateMachine {
+  public static final String LOG_TAG = FxAccountLoginStateMachine.class.getSimpleName();
+
+  public interface LoginStateMachineDelegate {
+    public FxAccountClient getClient();
+    public long getCertificateDurationInMilliseconds();
+    public long getAssertionDurationInMilliseconds();
+    public void handleTransition(Transition transition, State state);
+    public void handleFinal(State state);
+    public BrowserIDKeyPair generateKeyPair() throws NoSuchAlgorithmException;
+  }
+
+  public static class ExecuteDelegate {
+    protected final LoginStateMachineDelegate delegate;
+    protected final StateLabel desiredStateLabel;
+    // It's as difficult to detect arbitrary cycles as repeated states.
+    protected final Set<StateLabel> stateLabelsSeen = new HashSet<StateLabel>();
+
+    protected ExecuteDelegate(StateLabel initialStateLabel, StateLabel desiredStateLabel, LoginStateMachineDelegate delegate) {
+      this.delegate = delegate;
+      this.desiredStateLabel = desiredStateLabel;
+      this.stateLabelsSeen.add(initialStateLabel);
+    }
+
+    public FxAccountClient getClient() {
+      return delegate.getClient();
+    }
+
+    public long getCertificateDurationInMilliseconds() {
+      return delegate.getCertificateDurationInMilliseconds();
+    }
+
+    public long getAssertionDurationInMilliseconds() {
+      return delegate.getAssertionDurationInMilliseconds();
+    }
+
+    public BrowserIDKeyPair generateKeyPair() throws NoSuchAlgorithmException {
+      return delegate.generateKeyPair();
+    }
+
+    public void handleTransition(Transition transition, State state) {
+      // Always trigger the transition callback.
+      delegate.handleTransition(transition, state);
+
+      // Possibly trigger the final callback. We trigger if we're at our desired
+      // state, or if we've seen this state before.
+      StateLabel stateLabel = state.getStateLabel();
+      if (stateLabel == desiredStateLabel || stateLabelsSeen.contains(stateLabel)) {
+        delegate.handleFinal(state);
+        return;
+      }
+
+      // If this wasn't the last state, leave a bread crumb and move on to the
+      // next state.
+      stateLabelsSeen.add(stateLabel);
+      state.execute(this);
+    }
+  }
+
+  public void advance(State initialState, final StateLabel desiredStateLabel, final LoginStateMachineDelegate delegate) {
+    if (initialState.getStateLabel() == desiredStateLabel) {
+      // We're already where we want to be!
+      delegate.handleFinal(initialState);
+      return;
+    }
+    ExecuteDelegate executeDelegate = new ExecuteDelegate(initialState.getStateLabel(), desiredStateLabel, delegate);
+    initialState.execute(executeDelegate);
+  }
+}