[Mac][Material Design] Fix regression in position of chevron icon.

chrome/browser/ui/cocoa/bookmarks/bookmark_button_cell.mm

 // Copyright (c) 2011 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/bookmarks/bookmark_button_cell.h"
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_constants.h"
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_button.h"
@@ skipping 36 matching lines @@
 @implementation OffTheSideButtonCell
 
 - (BOOL)isOffTheSideButtonCell {
   return YES;
 }
 
 - (NSString*)accessibilityTitle {
   return l10n_util::GetNSString(IDS_ACCNAME_BOOKMARKS_CHEVRON);
 }
 
+- (NSRect)imageRectForBounds:(NSRect)theRect {
+  NSRect imageRect = [super imageRectForBounds:theRect];
+  if (ui::MaterialDesignController::IsModeMaterial()) {
+    // Make sure the chevron icon stays centered. Normally a bookmark bar item
+    // with no label has its icon placed at a fixed x-position.
+    CGFloat totalWidth = NSMaxX(theRect);
+    imageRect.origin.x = (totalWidth - [self image].size.width) / 2;
+  }
+  return imageRect;
+}
+
 @end
 
 @interface BookmarkButtonCell(Private)
 // Returns YES if the cell is the offTheSide button cell.
 - (BOOL)isOffTheSideButtonCell;
 - (void)configureBookmarkButtonCell;
 - (void)applyTextColor;
 // Returns the title the button cell displays. Note that a button cell can
 // have a title string assigned but it won't be visible if its image position
 // is NSImageOnly.
@@ skipping 383 matching lines @@
   const CGFloat kLineWidth = [controlView cr_lineWidth];
   if ([self isMaterialDesignButtonType] && ![self isFolderButtonCell] &&
       kLineWidth < 1) {
     return -kLineWidth;
   }
   return 0.0;
 }
 
 
 @end