Bug 1369815 - Set the display mode for standalone PWA r=droeh

MozReview-Commit-ID: EGCskj6pwkC

mobile/android/base/java/org/mozilla/gecko/webapps/WebAppActivity.java

@@ -182,6 +182,29 @@ public class WebAppActivity extends AppCompatActivity
         setRequestedOrientation(activityOrientation);
     }
 
+    private void updateDisplayMode(JSONObject manifest) {
+        String displayMode = manifest.optString("display");
+
+        GeckoViewSettings.DisplayMode mode;
+        switch (displayMode) {
+            case "standalone":
+                mode = GeckoViewSettings.DisplayMode.STANDALONE;
+                break;
+            case "fullscreen":
+                mode = GeckoViewSettings.DisplayMode.FULLSCREEN;
+                break;
+            case "minimal-ui":
+                mode = GeckoViewSettings.DisplayMode.MINIMAL_UI;
+                break;
+            case "browser":
+            default:
+                mode = GeckoViewSettings.DisplayMode.BROWSER;
+                break;
+        }
+
+        mGeckoView.getSettings().setInt(GeckoViewSettings.USE_DISPLAY_MODE, mode.value());
+    }
+
     private Integer readColorFromManifest(JSONObject manifest) {
         final String colorStr = manifest.optString("theme_color", null);
         if (colorStr != null) {