Fix inconsistent behavior of diff view when viewing binary files

In the new change screen, if the user clicks on a binary file in
the file list, the unified view is used.  Then when navigating to
a previous or next file that is not binary, the diff view stays in
the old unified setting.  It is only possible to get back to the
new side-by-side view by going back to the change screen and then
opening the non-binary file from there.

To keep consistent behavior of diff view, always use unified diff
for binary files.  Use the user's preference setting for non-binary
files.

Change-Id: Ie4ece4cb740df8a69cbf3d2d42e4b0fb05461520

gerrit-gwtui/src/main/java/com/google/gerrit/client/Dispatcher.java

@@ -529,7 +529,7 @@ public class Dispatcher {
     }
   }
 
-  private static boolean isChangeScreen2() {
+  public static boolean isChangeScreen2() {
     if (changeScreen2) {
       return true;
     }
@@ -593,6 +593,9 @@ public class Dispatcher {
           }
 
           if ("".equals(panel)) {
+            if (isChangeScreen2()) {
+              return new SideBySide2(baseId, id.getParentKey(), id.get());
+            }
             return new PatchScreen.SideBySide( //
                 id, //
                 patchIndex, //