Omnibox UI Experiments: Add border and shadow to narrow dropdown in Mac.

chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.h"
 
 #include <cmath>
 
 #include "base/feature_list.h"
 #include "base/mac/mac_util.h"
@@ skipping 157 matching lines @@
 
 void OmniboxPopupViewMac::CreatePopupIfNeeded() {
   if (!popup_) {
     popup_.reset(
         [[NSWindow alloc] initWithContentRect:ui::kWindowSizeDeterminedLater
                                     styleMask:NSBorderlessWindowMask
                                       backing:NSBackingStoreBuffered
                                         defer:NO]);
     [popup_ setBackgroundColor:[NSColor clearColor]];
     [popup_ setOpaque:NO];
+    bool narrow_popup =
+        base::FeatureList::IsEnabled(omnibox::kUIExperimentNarrowDropdown);
+    if (narrow_popup)
+      [popup_ setHasShadow:YES];
 
     // Use a flipped view to pin the matrix top the top left. This is needed
     // for animated resize.
     base::scoped_nsobject<FlippedView> contentView(
         [[FlippedView alloc] initWithFrame:NSZeroRect]);
     [popup_ setContentView:contentView];
 
     BOOL is_dark_theme = [[field_ window] hasDarkTheme];
 
     // View to draw a background beneath the matrix.
     background_view_.reset([[NSBox alloc] initWithFrame:NSZeroRect]);
     [background_view_ setBoxType:NSBoxCustom];
     [background_view_ setBorderType:NSNoBorder];
     [background_view_ setFillColor:BackgroundColor(is_dark_theme)];
     [background_view_ setContentViewMargins:NSZeroSize];
     [contentView addSubview:background_view_];
 
     matrix_.reset([[OmniboxPopupMatrix alloc] initWithObserver:this
                                                   forDarkTheme:is_dark_theme]);
     [background_view_ addSubview:matrix_];
 
-    top_separator_view_.reset(
-        [[OmniboxPopupTopSeparatorView alloc] initWithFrame:NSZeroRect]);
-    [contentView addSubview:top_separator_view_];
+    if (!narrow_popup) {
+      top_separator_view_.reset(
+          [[OmniboxPopupTopSeparatorView alloc] initWithFrame:NSZeroRect]);
+      [contentView addSubview:top_separator_view_];
 
-    bottom_separator_view_.reset([[OmniboxPopupBottomSeparatorView alloc]
-        initWithFrame:NSZeroRect
-         forDarkTheme:is_dark_theme]);
-    [contentView addSubview:bottom_separator_view_];
+      bottom_separator_view_.reset([[OmniboxPopupBottomSeparatorView alloc]
+          initWithFrame:NSZeroRect
+           forDarkTheme:is_dark_theme]);
+      [contentView addSubview:bottom_separator_view_];
+    }
 
     // TODO(dtseng): Ignore until we provide NSAccessibility support.
     [popup_ accessibilitySetOverrideValue:NSAccessibilityUnknownRole
                              forAttribute:NSAccessibilityRoleAttribute];
   }
 }
 
 void OmniboxPopupViewMac::PositionPopup(const CGFloat matrixHeight) {
   BrowserWindowController* controller =
       [BrowserWindowController browserWindowControllerForView:field_];
@@ skipping 132 matching lines @@
   return NSImageFromImageSkia(
       gfx::CreateVectorIcon(vector_icon, kIconSize, icon_color));
 }
 
 void OmniboxPopupViewMac::OpenURLForRow(size_t row,
                                         WindowOpenDisposition disposition) {
   DCHECK_LT(row, GetResult().size());
   omnibox_view_->OpenMatch(GetResult().match_at(row), disposition, GURL(),
                            base::string16(), row);
 }