mac: Add a missing animation context to bookmark bar controller.

The animation was not specifying an NSAnimationContext or duration, which meant
that the duration was not well defined. I used the same value that I observed
on my machine prior to my change. It seems a bit slow, but presumably it's the
value most users are seeing.

BUG=NONE
TEST=NONE

Review URL: https://codereview.chromium.org/110753004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243383 0039d316-1c4b-4281-b951-d872f2087c98

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

@@ -129,6 +129,7 @@ namespace {
 
 // Duration of the bookmark bar animations.
 const NSTimeInterval kBookmarkBarAnimationDuration = 0.12;
+const NSTimeInterval kDragAndDropAnimationDuration = 0.25;
 
 void RecordAppLaunch(Profile* profile, GURL url) {
   DCHECK(profile->GetExtensionService());
@@ -1939,6 +1940,9 @@ static BOOL ValueInRangeInclusive(CGFloat low, CGFloat value, CGFloat high) {
     }
     // Put all the buttons where they belong, with all buttons to the right
     // of the insertion point shuffling right to make space for it.
+    [NSAnimationContext beginGrouping];
+    [[NSAnimationContext currentContext]
+        setDuration:kDragAndDropAnimationDuration];
     for (NSButton* button in buttons_.get()) {
       // Hidden buttons get no space.
       if ([button isHidden])
@@ -1955,6 +1959,7 @@ static BOOL ValueInRangeInclusive(CGFloat low, CGFloat value, CGFloat high) {
       else
         [button setFrame:buttonFrame];
     }
+    [NSAnimationContext endGrouping];
   }
 }