Created the dialog offering the user to merge their account data or keep it

chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninActivity.java
new file mode 100644
index 0000000000000000000000000000000000000000..454fa693baf5e52989a729f1426f77d19c674c35
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountSigninActivity.java
@@ -0,0 +1,110 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.signin;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.support.v7.app.AppCompatActivity;
+import android.view.LayoutInflater;
+
+import org.chromium.base.metrics.RecordUserAction;
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.firstrun.ProfileDataCache;
+import org.chromium.chrome.browser.preferences.Preferences;
+import org.chromium.chrome.browser.preferences.PreferencesLauncher;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.sync.ui.ConfirmImportSyncDataFragment;
+import org.chromium.chrome.browser.sync.ui.ConfirmImportSyncDataFragment.ImportSyncType;
+import org.chromium.chrome.browser.sync.ui.ConfirmImportSyncDataFragment.Listener;
+import org.chromium.chrome.browser.sync.ui.SyncCustomizationFragment;
+
+/**
+ * An Activity displayed from the MainPreferences to allow the user to pick an account to
+ * sign in to.
+ */
+public class AccountSigninActivity extends AppCompatActivity
+        implements AccountSigninView.Listener, SigninManager.SignInCallback{
+    private static final String TAG = "AccountSigninFragment";
+
+    private static final String CONFIRM_IMPORT_SYNC_DATA_DIALOG_TAG =
+            "signin_import_data_tag";
+
+    private AccountSigninView mView;
+    private String mAccountName;
+    private boolean mShowSyncSettings = false;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {

[newt (away), 2016/02/25 06:25:53]

We need to make sure the native library is loaded here to handle this scenario:
 1. User opens Chrome, and launches this activity
 2. User goes to home screen and uses other apps for a while
 3. User goes back to Chrome via Android's recent apps list

In that case, in step 3, Android will recreate this activity (but not the
activities "underneath" it), and the native library be loaded... which would
lead to a crash.

See Preferences.onCreate() for an example of how to load the native library
synchronously.

[PEConn, 2016/02/25 14:19:51]

Done.

+        super.onCreate(savedInstanceState);
+
+        mView = (AccountSigninView) LayoutInflater.from(this).inflate(
+                R.layout.account_signin_view, null);
+        mView.init(new ProfileDataCache(this, Profile.getLastUsedProfile()));
+        mView.setListener(this);
+
+        setContentView(mView);
+    }
+
+    @Override
+    public void onAccountSelectionCanceled() {
+        finish();
+    }
+
+    @Override
+    public void onNewAccount() {
+        AccountAdder.getInstance().addAccount(this, AccountAdder.ADD_ACCOUNT_RESULT);
+    }
+
+    @Override
+    public void onAccountSelected(String accountName) {
+        mAccountName = accountName;
+
+    }
+
+    @Override
+    public void onDoneClicked() {
+        RecordUserAction.record("Signin_Signin_FromSettings");
+        SigninManager.get(this).signIn(mAccountName, null, this);

[newt (away), 2016/02/25 06:25:53]

We're using "non-interactive" sign-in here, which means that the managed account
warning will be bypassed (see SigninManager.signIn()). That doesn't seem right.
Is that intentional?

[PEConn, 2016/02/25 14:19:51]

I changed all of these back.

+    }
+
+    @Override
+    public void onSettingsClicked() {
+        RecordUserAction.record("Signin_Signin_FromSettings");
+        mShowSyncSettings = true;
+        SigninManager.get(this).signIn(mAccountName, null, this);
+    }
+
+    @Override
+    public void onFailedToSetForcedAccount(String forcedAccountName) {
+        assert false : "No forced accounts in account switching preferences.";
+
+    }
+
+    @Override
+    public void onSignInComplete() {
+        if (mShowSyncSettings) {
+            Intent intent = PreferencesLauncher.createIntentForSettingsPage(this,
+                    SyncCustomizationFragment.class.getName());
+            Bundle args = new Bundle();
+            args.putString(SyncCustomizationFragment.ARGUMENT_ACCOUNT, mAccountName);
+            intent.putExtra(Preferences.EXTRA_SHOW_FRAGMENT_ARGUMENTS, args);
+            startActivity(intent);
+        }
+
+        finish();
+    }
+
+    @Override
+    public void onSignInAborted() {
+        assert false : "Signin cannot be aborted when forced.";
+    }
+
+    @Override
+    public void onPreviousAccountFound(
+            String oldAccountName, String newAccountName, Listener callback) {
+        ConfirmImportSyncDataFragment.showNewInstance(oldAccountName, newAccountName,
+                ImportSyncType.PREVIOUS_DATA_FOUND, getFragmentManager(), callback);
+    }
+}