Mac: Don't relayout tabs if the tab strip's frame didn't change.

chrome/browser/ui/cocoa/browser_window_controller_private.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/browser_window_controller_private.h"
 
 #include <cmath>
 
 #include "base/command_line.h"
 #include "base/mac/mac_util.h"
@@ skipping 172 matching lines @@
 - (CGFloat)layoutTabStripAtMaxY:(CGFloat)maxY
                           width:(CGFloat)width
                      fullscreen:(BOOL)fullscreen {
   // Nothing to do if no tab strip.
   if (![self hasTabStrip])
     return maxY;
 
   NSView* tabStripView = [self tabStripView];
   CGFloat tabStripHeight = NSHeight([tabStripView frame]);
   maxY -= tabStripHeight;
-  [tabStripView setFrame:NSMakeRect(0, maxY, width, tabStripHeight)];
+  NSRect tabStripFrame = NSMakeRect(0, maxY, width, tabStripHeight);
 
   // In Yosemite fullscreen, manually add the fullscreen controls to the tab
   // strip.
   BOOL addControlsInFullscreen =
       [self isInAppKitFullscreen] && base::mac::IsOSYosemiteOrLater();
 
   // Set left indentation based on fullscreen mode status.
   CGFloat leftIndent = 0;
   if (!fullscreen || addControlsInFullscreen)
     leftIndent = [[tabStripController_ class] defaultLeftIndentForControls];
@@ skipping 49 matching lines @@
     if ([self shouldUseNewAvatarButton]) {
       // The new avatar button is to the left of the fullscreen button.
       // (The old avatar button is to the right).
       rightIndent += NSWidth([avatarButton frame]) + kAvatarRightOffset;
     }
   } else if ([self shouldShowAvatar]) {
     rightIndent += NSWidth([avatarButton frame]) + kAvatarRightOffset;
   }
   [tabStripController_ setRightIndentForControls:rightIndent];
 
-  // Go ahead and layout the tabs.
-  [tabStripController_ layoutTabsWithoutAnimation];
+  // It is undesirable to force tabs relayout when the tap strip's frame did
+  // not change, because it will interrupt tab animations in progress.
+  // In addition, there appears to be an AppKit bug on <10.9 where interrupting
+  // a tab animation resulted in the tab frame being the animator's target
+  // frame instead of the interrupting setFrame. (See http://crbug.com/415093)
+  if (!NSEqualRects(tabStripFrame, [tabStripView frame])){
+    [tabStripView setFrame:tabStripFrame];
+    [tabStripController_ layoutTabsWithoutAnimation];
+  }
 
   return maxY;
 }
 
 - (BOOL)placeBookmarkBarBelowInfoBar {
   // If we are currently displaying the NTP detached bookmark bar or animating
   // to/from it (from/to anything else), we display the bookmark bar below the
   // info bar.
   return [bookmarkBarController_ isInState:BookmarkBar::DETACHED] ||
          [bookmarkBarController_ isAnimatingToState:BookmarkBar::DETACHED] ||
@@ skipping 743 matching lines @@
 
       [CATransaction commit];
       hasAdjustedTabStripWhileEnteringAppKitFullscreen_ = YES;
     }
   } else {
     hasAdjustedTabStripWhileEnteringAppKitFullscreen_ = NO;
   }
 }
 
 @end  // @implementation BrowserWindowController(Private)