Fix download shelf item overflow on os x.

chrome/browser/cocoa/download_shelf_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/download_shelf_controller.h"
 
 #include "app/l10n_util.h"
 #include "base/mac_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/browser.h"
@@ skipping 28 matching lines @@
 
 @implementation DownloadShelfController
 
 - (id)initWithBrowser:(Browser*)browser
        resizeDelegate:(id<ViewResizer>)resizeDelegate {
   if ((self = [super initWithNibName:@"DownloadShelf"
                               bundle:mac_util::MainAppBundle()])) {
     resizeDelegate_ = resizeDelegate;
     shelfHeight_ = [[self view] bounds].size.height;
 
-    // Reset the download shelf's frame to zero.  It will be properly positioned
-    // and sized the first time we try to set its height.
-    [[self view] setFrame:NSZeroRect];
+    // Reset the download shelf's frame height to zero.  It will be properly
+    // positioned and sized the first time we try to set its height. (Just
+    // setting the rect to NSZeroRect does not work: it confuses Cocoa's view
+    // layout logic. If the shelf's width is too small, cocoa makes the download
+    // item container view wider than the browser window).
+    NSRect frame = [[self view] frame];
+    frame.size.height = 0;
+    [[self view] setFrame:frame];
 
     downloadItemControllers_.reset([[NSMutableArray alloc] init]);
 
-    // This calls show:, so it needs to be last.
     bridge_.reset(new DownloadShelfMac(browser, self));
   }
   return self;
 }
 
 - (void)awakeFromNib {
   // Initialize "Show all downloads" link.
 
   scoped_nsobject<NSMutableParagraphStyle> paragraphStyle(
       [[NSParagraphStyle defaultParagraphStyle] mutableCopy]);
@@ skipping 182 matching lines @@
     [self remove:[downloadItemControllers_ lastObject]];
   }
 
   // Finally, move the remaining items to the right. Skip the first item when
   // laying out the items, so that the longer animation duration we set up above
   // is not overwritten.
   [self layoutItems:YES];
 }
 
 @end