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

shell/android/apk/AndroidManifest.xml.jinja2

Index: shell/android/apk/AndroidManifest.xml.jinja2
diff --git a/shell/android/apk/AndroidManifest.xml.jinja2 b/shell/android/apk/AndroidManifest.xml.jinja2
index 11adbe6abbeda702a59eb47ea5ed38203957e69e..4b64ed206c8597fa112df983eb860515b099038b 100644
--- a/shell/android/apk/AndroidManifest.xml.jinja2
+++ b/shell/android/apk/AndroidManifest.xml.jinja2
@@ -27,10 +27,7 @@
         <activity android:name="org.chromium.mojo.shell.MojoShellActivity"
                   android:launchMode="standard"
                   android:documentLaunchMode="none"
-                  android:theme="@android:style/Theme.Holo.Light.NoActionBar"
-                  android:configChanges="orientation|keyboardHidden|keyboard|screenSize"
-                  android:windowSoftInputMode="adjustPan"
-                  android:hardwareAccelerated="true">
+                  android:theme="@android:style/Theme.NoDisplay">
             <intent-filter>
                 <!-- A mojo://host/path url will load the app at the
                      https://host/path URL.
@@ -41,6 +38,12 @@
                 <category android:name="android.intent.category.BROWSABLE"/>
             </intent-filter>
         </activity>
+        <activity android:name="org.chromium.mojo.shell.ViewportActivity"
+                  android:theme="@android:style/Theme.Holo.Light.NoActionBar"
+                  android:configChanges="orientation|keyboardHidden|keyboard|screenSize"
+                  android:windowSoftInputMode="adjustPan"
+                  android:hardwareAccelerated="true">
+        </activity>
         <activity android:name="org.chromium.mojo.shell.NfcReceiverActivity"
                   android:theme="@android:style/Theme.NoDisplay" >
             <intent-filter>