Allow native_viewport to create new native windows on demand on Android.

services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java

Index: services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java
diff --git a/services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java b/services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java
index fabcb081c574382ffe5c7e927eaa4b3ae52e4914..1b1ef9bf5cf688f9bd710921777d20bc530a0713 100644
--- a/services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java
+++ b/services/native_viewport/android/src/org/chromium/mojo/PlatformViewportAndroid.java
@@ -6,6 +6,7 @@ package org.chromium.mojo;
 
 import android.app.Activity;
 import android.content.Context;
+import android.content.Intent;
 import android.view.MotionEvent;
 import android.view.Surface;
 import android.view.SurfaceHolder;
@@ -18,6 +19,7 @@ import org.chromium.base.ApplicationStatus;
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
 import org.chromium.mojo.keyboard.KeyboardServiceImpl;
+import org.chromium.mojo.shell.ViewportActivity;
 
 /**
  * Exposes SurfaceView to native code.
@@ -30,13 +32,23 @@ public class PlatformViewportAndroid extends SurfaceView {
 
     @CalledByNative
     public static PlatformViewportAndroid create(long nativeViewport) {
-        Activity activity = ApplicationStatus.getLastTrackedFocusedActivity();
+        Activity activity = ViewportActivity.getNextUnattachedActivity();
         PlatformViewportAndroid rv = new PlatformViewportAndroid(activity, nativeViewport);
         KeyboardServiceImpl.setActiveView(rv);
         activity.setContentView(rv);
         return rv;
     }
 
+    @CalledByNative
+    public static void createNativeWindow() {
+        final Context context = ApplicationStatus.getApplicationContext();
+        final Intent newDocumentIntent = new Intent(context, ViewportActivity.class);
+        newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT);
+        newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
+        newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        context.startActivity(newDocumentIntent);
+    }
+
     public PlatformViewportAndroid(Context context, long nativeViewport) {
         super(context);