Restore r25049 (back out r25295) to isolate it as the cause of bug 20872

chrome/browser/cocoa/tab_strip_controller.mm

 // Copyright (c) 2009 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/cocoa/tab_strip_controller.h"
 
 #include "app/l10n_util.h"
 #include "base/mac_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/app/chrome_dll_resource.h"
@@ skipping 401 matching lines @@
     } else {
       // If our left edge is to the left of the placeholder's left, but our mid
       // is to the right of it we should slide over to make space for it.
       if (placeholderTab_ && gap < 0 && NSMidX(tabFrame) > minX) {
         gap = i;
         offset += NSWidth(tabFrame);
         offset -= kTabOverlap;
         tabFrame.origin.x = offset;
       }
 
-      // Animate the tab in by putting it below the horizon.
-      if (newTab && visible && animate) {
+      // Animate the tab in by putting it below the horizon, but don't bother
+      // if we only have 1 tab.
+      BOOL shouldAnimate = animate && [tabContentsArray_ count] > 1;
+      if (newTab && visible && shouldAnimate) {
         [[tab view] setFrame:NSOffsetRect(tabFrame, 0, -NSHeight(tabFrame))];
       }
 
       // Set the width. Selected tabs are slightly wider when things get
       // really small and thus we enforce a different minimum width.
       tabFrame.size.width =
           [tab selected] ? MAX(baseTabWidth, kMinSelectedTabWidth) :
                            baseTabWidth;
 
       // Check the frame by identifier to avoid redundant calls to animator.
       id frameTarget = visible && animate ? [[tab view] animator] : [tab view];
       NSValue *identifier = [NSValue valueWithPointer:[tab view]];
       NSValue *oldTargetValue = [targetFrames_ objectForKey:identifier];
       if (!oldTargetValue ||
           !NSEqualRects([oldTargetValue rectValue], tabFrame)) {
         [frameTarget setFrame:tabFrame];
         [targetFrames_ setObject:[NSValue valueWithRect:tabFrame]
                           forKey:identifier];
       }
       enclosingRect = NSUnionRect(tabFrame, enclosingRect);
     }
 
     offset += NSWidth(tabFrame);
     offset -= kTabOverlap;
     i++;
   }
 
   // Hide the new tab button if we're explicitly told to. It may already
-  // be hidden, doing it again doesn't hurt.
+  // be hidden, doing it again doesn't hurt. Otherwise position it
+  // appropriately, showing it if necessary.
   if (forceNewTabButtonHidden_) {
     [newTabButton_ setHidden:YES];
   } else {
     NSRect newTabNewFrame = [newTabButton_ frame];
     // We've already ensured there's enough space for the new tab button
     // so we don't have to check it against the available width. We do need
     // to make sure we put it after any placeholder.
     newTabNewFrame.origin = NSMakePoint(offset, 0);
     newTabNewFrame.origin.x = MAX(newTabNewFrame.origin.x,
                                   NSMaxX(placeholderFrame_)) +
                                       kNewTabButtonOffset;
-    if (i > 0 && [newTabButton_ isHidden]) {
-      id target = animate ? [newTabButton_ animator] : newTabButton_;
-      [target setHidden:NO];
-    }
+    if ([tabContentsArray_ count])
+      [newTabButton_ setHidden:NO];
 
     if (!NSEqualRects(newTabTargetFrame_, newTabNewFrame)) {
       [newTabButton_ setFrame:newTabNewFrame];
       newTabTargetFrame_ = newTabNewFrame;
       // Move the new tab button into place.
     }
   }
 
   [NSAnimationContext endGrouping];
   [dragBlockingView_ setFrame:enclosingRect];
@@ skipping 476 matching lines @@
   BrowserWindowController* controller =
       (BrowserWindowController*)[[switchView_ window] windowController];
   DCHECK(index >= 0);
   if (index >= 0) {
     [controller setTab:[self viewAtIndex:index] isDraggable:YES];
   }
 }
 
 
 @end