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, //

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PatchTable.java

@@ -22,6 +22,7 @@ import com.google.gerrit.client.ui.ListenableAccountDiffPreference;
 import com.google.gerrit.client.ui.NavigationTable;
 import com.google.gerrit.client.ui.PatchLink;
 import com.google.gerrit.common.data.PatchSetDetail;
+import com.google.gerrit.reviewdb.client.AccountGeneralPreferences.DiffView;
 import com.google.gerrit.reviewdb.client.Patch;
 import com.google.gerrit.reviewdb.client.Patch.ChangeType;
 import com.google.gerrit.reviewdb.client.Patch.Key;
@@ -244,21 +245,23 @@ public class PatchTable extends Composite {
   /**
    * @return a link to the the given patch.
    * @param index The patch to link to
-   * @param patchType The type of patch display
+   * @param screenType The screen type of patch display
    * @param before A string to display at the beginning of the href text
    * @param after A string to display at the end of the href text
    */
-  public PatchLink createLink(int index, PatchScreen.Type patchType,
+  public PatchLink createLink(int index, PatchScreen.Type screenType,
       SafeHtml before, SafeHtml after) {
     Patch patch = patchList.get(index);
 
     Key thisKey = patch.getKey();
     PatchLink link;
-    if (patchType == PatchScreen.Type.SIDE_BY_SIDE) {
+
-      link = new PatchLink.SideBySide("", base, thisKey, index, detail, this);
+    if (isUnifiedPatchLink(patch, screenType)) {
-    } else {
       link = new PatchLink.Unified("", base, thisKey, index, detail, this);
+    } else {
+      link = new PatchLink.SideBySide("", base, thisKey, index, detail, this);
     }
+
     SafeHtmlBuilder text = new SafeHtmlBuilder();
     text.append(before);
     text.append(getFileNameOnly(patch));
@@ -267,6 +270,16 @@ public class PatchTable extends Composite {
     return link;
   }
 
+  private static boolean isUnifiedPatchLink(final Patch patch,
+      final PatchScreen.Type screenType) {
+    if (Dispatcher.isChangeScreen2()) {
+      return (patch.getPatchType().equals(PatchType.BINARY)
+          || Gerrit.getUserAccount().getGeneralPreferences().getDiffView()
+          .equals(DiffView.UNIFIED_DIFF));
+    }
+    return screenType == PatchScreen.Type.UNIFIED;
+  }
+
   private static String getFileNameOnly(Patch patch) {
     // Note: use '/' here and not File.pathSeparator since git paths
     // are always separated by /