[ios] Extend WebStateListObserver amd WebStateListDelegate APIs.

ios/chrome/browser/tabs/tab_model_observers_bridge.mm

Index: ios/chrome/browser/tabs/tab_model_observers_bridge.mm
diff --git a/ios/chrome/browser/tabs/tab_model_observers_bridge.mm b/ios/chrome/browser/tabs/tab_model_observers_bridge.mm
index df7be5f10cb365ea4928168c57798085d5734600..2fc02d26f9a5b88501a8fc3b45141983c32d1ffa 100644
--- a/ios/chrome/browser/tabs/tab_model_observers_bridge.mm
+++ b/ios/chrome/browser/tabs/tab_model_observers_bridge.mm
@@ -33,11 +33,11 @@
 
 - (void)webStateList:(WebStateList*)webStateList
     didInsertWebState:(web::WebState*)webState
-              atIndex:(int)index {
-  DCHECK_GE(index, 0);
+              atIndex:(int)atIndex {

[rohitrao (ping after 24h), 2017/03/24 01:20:52]

Why this change?

[sdefresne, 2017/03/24 09:26:18]

Just consistency when naming the parameter (as detailed in the CL description).
I called it |index| in half the methods and |atIndex| in the others. I settled
on |atIndex| because it seemed more common on the old code base, but I can use
|index| if you prefer.

[rohitrao (ping after 24h), 2017/03/24 14:18:09]

I prefer index, but I don't feel strongly.

+  DCHECK_GE(atIndex, 0);
   [_tabModelObservers tabModel:_tabModel
                   didInsertTab:LegacyTabHelper::GetTabForWebState(webState)
-                       atIndex:static_cast<NSUInteger>(index)
+                       atIndex:static_cast<NSUInteger>(atIndex)
                   inForeground:NO];
   [_tabModelObservers tabModelDidChangeTabCount:_tabModel];
 }
@@ -57,21 +57,21 @@
 - (void)webStateList:(WebStateList*)webStateList
     didReplaceWebState:(web::WebState*)oldWebState
           withWebState:(web::WebState*)newWebState
-               atIndex:(int)index {
-  DCHECK_GE(index, 0);
+               atIndex:(int)atIndex {
+  DCHECK_GE(atIndex, 0);
   [_tabModelObservers tabModel:_tabModel
                  didReplaceTab:LegacyTabHelper::GetTabForWebState(oldWebState)
                        withTab:LegacyTabHelper::GetTabForWebState(newWebState)
-                       atIndex:static_cast<NSUInteger>(index)];
+                       atIndex:static_cast<NSUInteger>(atIndex)];
 }
 
 - (void)webStateList:(WebStateList*)webStateList
     didDetachWebState:(web::WebState*)webState
-              atIndex:(int)index {
-  DCHECK_GE(index, 0);
+              atIndex:(int)atIndex {
+  DCHECK_GE(atIndex, 0);
   [_tabModelObservers tabModel:_tabModel
                   didRemoveTab:LegacyTabHelper::GetTabForWebState(webState)
-                       atIndex:static_cast<NSUInteger>(index)];
+                       atIndex:static_cast<NSUInteger>(atIndex)];
   [_tabModelObservers tabModelDidChangeTabCount:_tabModel];
 }