Fix flickering Mac app launcher progress bar on <10.9

On Mavericks, the app lanucher subviews need to have access to a
compositing layer they can share. Otherwise the compositor makes tearing
artifacts. However, doing this on Mountain Lion or earlier results in
flickering whilst an item is installing IF the app launcher menu is also
opened - a different Apple bug.

This CL restricts the fix for the tearing to Mavericks or later.

BUG=362547
TEST=Install a large app from the webstore on Mountain Lion (10.8) or
earlier. Open the app launcher menu. The progress bar should not
flicker.

Review URL: https://codereview.chromium.org/263613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@267189 0039d316-1c4b-4281-b951-d872f2087c98

ui/app_list/cocoa/app_list_view_controller.mm

@@ -5,6 +5,7 @@
 #import "ui/app_list/cocoa/app_list_view_controller.h"
 
 #include "base/mac/foundation_util.h"
+#include "base/mac/mac_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "skia/ext/skia_utils_mac.h"
@@ -199,9 +200,12 @@ -(void)loadAndSetView {
   contentsView_.reset([[FlippedView alloc] initWithFrame:contentsRect]);
 
   // The contents view contains animations both from an NSCollectionView and the
-  // app list's own transitive drag layers. Ensure the subviews have access to
-  // a compositing layer they can share.
-  [contentsView_ setWantsLayer:YES];
+  // app list's own transitive drag layers. On Mavericks, the subviews need to
+  // have access to a compositing layer they can share. Otherwise the compositor
+  // makes tearing artifacts. However, doing this on Mountain Lion or earler
+  // results in flickering whilst an item is installing.
+  if (base::mac::IsOSMavericksOrLater())
+    [contentsView_ setWantsLayer:YES];
 
   backgroundView_.reset(
       [[BackgroundView alloc] initWithFrame: