Bug 1350718 - Post: Name the special value -1 used to indicate a new tab should be appended. r=maliu

MozReview-Commit-ID: 7r8cHItW4wG

--HG--
extra : rebase_source : b7ea5736f706a126f553d6c2eddc314ee4f5f011

mobile/android/base/java/org/mozilla/gecko/Tabs.java

@@ -81,6 +81,8 @@ public class Tabs implements BundleEventListener {
     private static final long PERSIST_TABS_AFTER_MILLISECONDS = 1000 * 2;
 
     public static final int INVALID_TAB_ID = -1;
+    // Used to indicate a new tab should be appended to the current tabs.
+    public static final int NEW_LAST_INDEX = -1;
 
     private static final AtomicInteger sTabId = new AtomicInteger(0);
     private volatile boolean mInitialTabsAdded;
@@ -260,10 +262,17 @@ public class Tabs implements BundleEventListener {
         return tab;
     }
 
-    // Return the index, among those tabs of the chosen type whose privacy setting matches
-    // isPrivate, of the tab at position index in mOrder.  Returns -1, for "new last tab",
-    // when index is -1.
+    /**
+     * Return the index, among those tabs of the chosen {@code type} whose privacy setting matches
+     * {@code isPrivate}, of the tab at position {@code index} in {@code mOrder}.  Returns
+     * {@code NEW_LAST_INDEX} when {@code index} is {@code NEW_LAST_INDEX} or no matches were
+     * found.
+     */
     private int getPrivacySpecificTabIndex(int index, boolean isPrivate, TabType type) {
+        if (index == NEW_LAST_INDEX) {
+            return NEW_LAST_INDEX;
+        }
+
         int privacySpecificIndex = -1;
         for (int i = 0; i <= index; i++) {
             final Tab tab = mOrder.get(i);
@@ -271,7 +280,7 @@ public class Tabs implements BundleEventListener {
                 privacySpecificIndex++;
             }
         }
-        return privacySpecificIndex;
+        return privacySpecificIndex > -1 ? privacySpecificIndex : NEW_LAST_INDEX;
     }
 
     public synchronized void removeTab(int id) {
@@ -1022,7 +1031,7 @@ public class Tabs implements BundleEventListener {
             String tabUrl = (url != null && Uri.parse(url).getScheme() != null) ? url : null;
 
             // Add the new tab to the end of the tab order.
-            final int tabIndex = -1;
+            final int tabIndex = NEW_LAST_INDEX;
 
             tabToSelect = addTab(tabId, tabUrl, external, parentId, url, isPrivate, tabIndex, type);
             tabToSelect.setDesktopMode(desktopMode);

mobile/android/base/java/org/mozilla/gecko/tabs/TabsLayout.java

@@ -106,8 +106,7 @@ public abstract class TabsLayout extends RecyclerView
         switch (msg) {
             case ADDED:
                 int tabIndex = Integer.parseInt(data);
-                // A tabIndex of -1 means "add a new last tab".
-                tabIndex = tabIndex == -1 ? tabsAdapter.getItemCount() : tabIndex;
+                tabIndex = tabIndex == Tabs.NEW_LAST_INDEX ? tabsAdapter.getItemCount() : tabIndex;
                 tabsAdapter.notifyTabInserted(tab, tabIndex);
                 if (addAtIndexRequiresScroll(tabIndex)) {
                     // (The SELECTED tab is updated *after* this call to ADDED, so don't just call