Make the edge where BackgroundGradientView draws a divider selectable.

chrome/browser/ui/cocoa/download/download_shelf_view_cocoa.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.
 
 #import "chrome/browser/ui/cocoa/download/download_shelf_view_cocoa.h"
 
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/themes/theme_service.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 #import "chrome/browser/ui/cocoa/view_id_util.h"
 #import "ui/base/cocoa/nsview_additions.h"
 #include "ui/base/material_design/material_design_controller.h"
 
 @implementation DownloadShelfView
 
 // For programmatic instantiations in unit tests.
 - (id)initWithFrame:(NSRect)frameRect {
   if ((self = [super initWithFrame:frameRect])) {
-    [self setShowsDivider:NO];
+    [self commonInit];
   }
   return self;
 }
 
 // For nib instantiations in production.
 - (id)initWithCoder:(NSCoder*)decoder {
   if ((self = [super initWithCoder:decoder])) {
-    [self setShowsDivider:NO];
+    [self commonInit];
   }
   return self;
 }
 
-- (NSColor*)strokeColor {
-  const ui::ThemeProvider* themeProvider = [[self window] themeProvider];
-  if (!themeProvider) {
-    return [NSColor blackColor];
-  }
-  if (!ui::MaterialDesignController::IsModeMaterial()) {
-    BOOL isActive = [[self window] isMainWindow];
-    return themeProvider->GetNSColor(
-        isActive ? ThemeProperties::COLOR_TOOLBAR_STROKE :
-                   ThemeProperties::COLOR_TOOLBAR_STROKE_INACTIVE);
-  }
-  return themeProvider->GetNSColor(
-             ThemeProperties::COLOR_DETACHED_BOOKMARK_BAR_SEPARATOR);
+- (void)commonInit {
+  self.divider = BackgroundGradientViewDivider::Top;
+  self.showsDivider = YES;
 }
 
 - (NSPoint)patternPhase {
   // We want our backgrounds for the shelf to be phased from the upper
   // left hand corner of the view. Offset it by tab height so that the
   // background matches the toolbar background.
   return NSMakePoint(
       0, NSHeight([self bounds]) + [TabStripController defaultTabHeight]);
 }
 
-- (void)drawRect:(NSRect)dirtyRect {
-  [super drawRect:dirtyRect];
-
-  // Draw top stroke
-  NSRect borderRect, contentRect;
-  NSDivideRect([self bounds], &borderRect, &contentRect, [self cr_lineWidth],
-               NSMaxYEdge);
-  if (NSIntersectsRect(borderRect, dirtyRect)) {
-    [[self strokeColor] set];
-    NSRectFillUsingOperation(NSIntersectionRect(borderRect, dirtyRect),
-                             NSCompositeSourceOver);
-  }
-
-  // Draw the top highlight
-  borderRect.origin.y -= [self cr_lineWidth];
-  if (NSIntersectsRect(borderRect, dirtyRect)) {
-    const ui::ThemeProvider* themeProvider = [[self window] themeProvider];
-    if (themeProvider) {
-      int resourceName = themeProvider->UsingSystemTheme()
-                             ? ThemeProperties::COLOR_TOOLBAR_BEZEL
-                             : ThemeProperties::COLOR_TOOLBAR;
-      NSColor* highlightColor = themeProvider->GetNSColor(resourceName);
-      if (highlightColor) {
-        [highlightColor set];
-        NSRectFillUsingOperation(NSIntersectionRect(borderRect, dirtyRect),
-                                 NSCompositeSourceOver);
-      }
-    }
-  }
-}

[Nico, 2016/09/12 13:45:55]

Is this appearance-preserving?

[Sidney San Martín, 2016/09/14 17:46:59]

It is now, as far as I can tell.

-
 // Mouse down events on the download shelf should not allow dragging the parent
 // window around.
 - (BOOL)mouseDownCanMoveWindow {
   return NO;
 }
 
 - (ViewID)viewID {
   return VIEW_ID_DOWNLOAD_SHELF;
 }
 
 - (BOOL)isOpaque {
   return YES;
 }
 
 @end