[Mac] Fix tab dragging in RTL

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 1738 matching lines @@
 }
 
 - (int)indexOfPlaceholder {
   // Use |tabArray_| here instead of the tab strip count in order to get the
   // correct index when there are closing tabs to the left of the placeholder.
   const int count = [tabArray_ count];
 
   // No placeholder, return the end of the strip.
   if (placeholderTab_ == nil)
     return count;
-
-  double placeholderX = placeholderFrame_.origin.x;
+  BOOL isRTL = cocoa_l10n_util::ShouldDoExperimentalRTLLayout();
+  double placeholderX =
+      isRTL ? NSMaxX(placeholderFrame_) : placeholderFrame_.origin.x;
   int index = 0;
   int location = 0;
   while (index < count) {
     // Ignore closing tabs for simplicity. The only drawback of this is that
     // if the placeholder is placed right before one or several contiguous
     // currently closing tabs, the associated TabController will start at the
     // end of the closing tabs.
     if ([closingControllers_ containsObject:[tabArray_ objectAtIndex:index]]) {
       index++;
       continue;
     }
     NSView* curr = [self viewAtIndex:index];
     // The placeholder tab works by changing the frame of the tab being dragged
     // to be the bounds of the placeholder, so we need to skip it while we're
     // iterating, otherwise we'll end up off by one.  Note This only effects
     // dragging to the right, not to the left.
     if (curr == placeholderTab_) {
       index++;
       continue;
     }
-    if (placeholderX <= NSMinX([curr frame]))
+    if (isRTL ? placeholderX >= NSMaxX([curr frame])
+              : placeholderX <= NSMinX([curr frame]))
       break;
     index++;
     location++;
   }
   return location;
 }
 
 // Move the given tab at index |from| in this window to the location of the
 // current placeholder.
 - (void)moveTabFromIndex:(NSInteger)from {
@@ skipping 587 matching lines @@
   for (int i = 0; i < tabStripModel_->count(); i++) {
     [self updateIconsForContents:tabStripModel_->GetWebContentsAt(i) atIndex:i];
   }
 }
 
 - (void)setVisualEffectsDisabledForFullscreen:(BOOL)fullscreen {
   [tabStripView_ setVisualEffectsDisabledForFullscreen:fullscreen];
 }
 
 @end