First step in enabling creating tabs without an Activity on Android.

chrome/android/java/src/org/chromium/chrome/browser/ServiceTabCreator.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ServiceTabCreator.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ServiceTabCreator.java b/chrome/android/java/src/org/chromium/chrome/browser/ServiceTabCreator.java
new file mode 100644
index 0000000000000000000000000000000000000000..2feb4d098beb499dcf2755550336906388a79a02
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ServiceTabCreator.java
@@ -0,0 +1,81 @@
+// Copyright 2015 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;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.content.pm.PackageManager.NameNotFoundException;
+import android.net.Uri;
+import android.util.Log;
+
+import org.chromium.base.CalledByNative;
+
+/**
+ * Tab Creator to be used from background Android Services, when it is not known whether an
+ * Activity is available. It works by sending an intent to launch a new tab, and then getting

[Miguel Garcia, 2015/02/03 16:58:40]

It does no work like this yet right? Perhaps keep the comment describing the
current functionality and change it as you itereate.

[Peter Beverloo, 2015/02/03 17:24:54]

Done. I added a TODO.

+ * confirmation from the Activity that the tab has been created.
+ */
+public class ServiceTabCreator {
+    private static final String TAG = ServiceTabCreator.class.getSimpleName();
+
+    private static final String BROWSER_ACTIVITY_KEY =
+            "org.chromium.chrome.browser.BROWSER_ACTIVITY";
+
+    private final long mNativeServiceTabCreator;
+    private final Context mContext;
+
+    @CalledByNative
+    private static ServiceTabCreator create(long nativeServiceTabCreator, Context context) {

[Miguel Garcia, 2015/02/03 16:58:40]

shouldn't we make this a singleton so that we have only one of this hanging
around instead of one per call? There is only one natveServiceTabCreator 

[Peter Beverloo, 2015/02/03 17:24:54]

What else would initialize it, given @CalledByNative to a Singleton'd class? Do
you think the overhead of keeping a sInstance member around (+ errors and
logging) for the sake of asserting that it's a singleton is worth it? I don't
think it is.

+        return new ServiceTabCreator(nativeServiceTabCreator, context);
+    }
+
+    private ServiceTabCreator(long nativeServiceTabCreator, Context context) {
+        mNativeServiceTabCreator = nativeServiceTabCreator;
+        mContext = context;
+    }
+
+    /**
+     * Launches the browser activity and creates a new tab for |url|.
+     *
+     * @param url The URL to be opened in a new tab.
+     */
+    @CalledByNative
+    private void createTab(String url) {

[Miguel Garcia, 2015/02/03 16:58:40]

perhaps rename it to launchTab, it would be mode descriptive.

[Peter Beverloo, 2015/02/03 17:24:54]

Done.

+        Intent intent = new Intent(mContext, getBrowserActivityClassFromManifest());

[Miguel Garcia, 2015/02/03 16:58:40]

perhaps get the class first and fail gracefully if
getBrowserActivityClassFromManifest returns null.

[Peter Beverloo, 2015/02/03 17:24:54]

The only realistic failure-case for gBACFM() is that the manifest key has not
been set correctly, nothing based on user-input. I'd argue that we want that to
explode so that we can catch it in tests prior to rolling it out to users?

+        intent.setAction(Intent.ACTION_MAIN);
+        intent.addCategory(Intent.CATEGORY_LAUNCHER);
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        intent.setData(Uri.parse(url));
+
+        // TODO(peter): Add the referer.
+
+        mContext.startActivity(intent);
+    }
+
+    /**
+     * Reads the BROWSER_ACTIVITY name from the meta data in the Android Manifest file.
+     *
+     * @return Class for the browser activity to use when creating tabs.
+     */
+    private Class<?> getBrowserActivityClassFromManifest() {
+        try {
+            ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
+                    mContext.getPackageName(), PackageManager.GET_META_DATA);
+            String className = info.metaData.getString(BROWSER_ACTIVITY_KEY);
+
+            return Class.forName(className);
+
+        } catch (NameNotFoundException e) {
+            // Context.getPackageName() refers to an invalid package name, which is not possible.

[Miguel Garcia, 2015/02/03 16:58:40]

You might still want to log it just in case.

[Peter Beverloo, 2015/02/03 17:24:54]

Done. I also removed the comments.

+        } catch (ClassNotFoundException e) {
+            // The value of BROWSER_ACTIVITY does not refer to an existing class.
+            Log.e(TAG, "Invalid value for BROWSER_ACTIVITY in the Android manifest file.");
+        }
+
+        return null;
+    }
+}