Add pathway to auto-migrate users when Chrome launches

chrome/android/java/src/org/chromium/chrome/browser/document/UpgradeActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/document/UpgradeActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/document/UpgradeActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/document/UpgradeActivity.java
new file mode 100644
index 0000000000000000000000000000000000000000..059b03af124518c9073eb48492136d29b7c23edb
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/document/UpgradeActivity.java
@@ -0,0 +1,102 @@
+// 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.document;
+
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
+import android.support.v7.app.AppCompatActivity;
+
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.tabmodel.DocumentModeAssassin;
+import org.chromium.chrome.browser.tabmodel.DocumentModeAssassin.DocumentModeAssassinObserver;
+import org.chromium.chrome.browser.util.IntentUtils;
+
+/**
+ * Activity that appears when users are being upgraded to another version of Chrome.
+ *
+ * TODO(dfalcantara): Do we need to worry about onNewIntent()?
+ */
+public class UpgradeActivity extends AppCompatActivity {
+    public static final String EXTRA_INTENT_TO_REFIRE =
+            "org.chromium.chrome.browser.document.INTENT_TO_REFIRE";
+
+    private static final long MIN_MS_TO_DISPLAY_ACTIVITY = 500;
+
+    private final Handler mHandler;
+    private final DocumentModeAssassinObserver mObserver;
+
+    private boolean mHasStartedMigration;
+    private long mStartTimestamp;
+
+    public static void launchInstance(Context context, Intent originalIntent) {
+        Intent intent = new Intent();
+        intent.setClass(context, UpgradeActivity.class);
+        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        intent.putExtra(UpgradeActivity.EXTRA_INTENT_TO_REFIRE, originalIntent);
+        context.startActivity(intent);
+    }
+
+    public UpgradeActivity() {
+        mHandler = new Handler(Looper.getMainLooper());
+
+        mObserver = new DocumentModeAssassinObserver() {
+            private boolean mAlreadyRan;
+
+            @Override
+            public void onStageChange(int newStage) {
+                if (newStage != DocumentModeAssassin.STAGE_DONE || mAlreadyRan) return;
+                mAlreadyRan = true;

[Ted C, 2016/03/25 17:38:05]

how could we hit the already ran case?  Or is this just a cautious check?

[gone, 2016/03/25 22:05:41]

Paranoia.  I'd suggest asserting, but it seems like a bad idea to force a crash
on an upgrade path when we can't even test if asserts are working correctly on
current Android builds.

+                DocumentModeAssassin.getInstance().removeObserver(this);
+
+                // Always post to avoid any issues that could arise from firing the Runnable
+                // while other Observers are being alerted.
+                long msElapsed = System.currentTimeMillis() - mStartTimestamp;
+                long msRemaining = Math.max(0, MIN_MS_TO_DISPLAY_ACTIVITY - msElapsed);
+                Runnable continueExecutionRunnable = new Runnable() {
+                    @Override
+                    public void run() {
+                        continueExecution();

[Ted C, 2016/03/25 17:38:05]

if the activity is destroyed before this is called, will this barf?  Just
wondering if we have to track that to avoid the good ol' android crashes.

[gone, 2016/03/25 22:05:42]

Reshuffled code around a bit to make it more robust.

+                    }
+                };
+                mHandler.postDelayed(continueExecutionRunnable, msRemaining);
+            }
+        };
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        // Migration might have finished in the background.
+        DocumentModeAssassin assassin = DocumentModeAssassin.getInstance();
+        if (!DocumentModeAssassin.isMigrationNecessary()
+                || assassin.getStage() == DocumentModeAssassin.STAGE_DONE) {
+            continueExecution();
+            return;
+        }
+
+        // Kick off migration and wait for it to finish.
+        setContentView(R.layout.upgrade_activity);
+        mStartTimestamp = System.currentTimeMillis();
+        assassin.addObserver(mObserver);
+        assassin.migrateFromDocumentToTabbedMode();
+    }
+
+    private void continueExecution() {
+        finish();
+
+        // Fire the Intent that caused the user to end up on the migration pathway.
+        Intent intent =
+                (Intent) IntentUtils.safeGetParcelableExtra(getIntent(), EXTRA_INTENT_TO_REFIRE);
+        if (intent != null) {
+            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_NEW_DOCUMENT);
+            startActivity(intent);
+            overridePendingTransition(android.R.anim.fade_in, 0);
+        }

[Ted C, 2016/03/25 17:38:05]

should we try to launch a main intent otherwise?

[gone, 2016/03/25 22:05:41]

Done.

+    }
+}