Mac: Restore the show animation and subpixel AA for extension permissions prompts

chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm

Index: chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm b/chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm
index 6654389b31e7d075878f753b21a903517b726380..4952dbeb8388709b29aee50d63d47aa0b8e0c6aa 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_install_view_controller.mm
@@ -277,6 +277,14 @@ bool HasAttribute(id item, CellAttributesMask attributeMask) {
 }
 
 - (void)awakeFromNib {
+  // Since linking to 10.10, |outlineView_| needs an explicit background to
+  // ensure subpixel antialiasing is enabled for the permissions text. At the
+  // same time, the animation that shows the prompt breaks whenever the scroll
+  // view is present. Giving the scroll view a layer restores the animation, and
+  // since its contents has an opaque background, subpixel AA isn't affected.
+  [[outlineView_ enclosingScrollView] setWantsLayer:YES];
+  [outlineView_ setBackgroundColor:[NSColor whiteColor]];
+
   // Set control labels.
   [titleField_ setStringValue:base::SysUTF16ToNSString(
       prompt_->GetDialogTitle())];