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.dividerEdge = NSRectEdgeMaxY;
   }
   return self;
 }
 
 // For nib instantiations in production.
 - (id)initWithCoder:(NSCoder*)decoder {
   if ((self = [super initWithCoder:decoder])) {
-    [self setShowsDivider:NO];
+    self.dividerEdge = NSRectEdgeMaxY;
   }
   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);
-}
-
 - (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
+  // Draw the top highlight
   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
+  NSDivideRect([self bounds], &borderRect, &contentRect,
+               [self cr_lineWidth] * 2, NSMaxYEdge);

[Nico, 2016/09/14 18:06:37]

is the `* 2` here correct? from what I understand, the superclass now draws the
stroke, and we only draw the the highlight below that here now. the highlight
was one cr_lineWidth high before; now it looks like it's two cr_lineWidth high
as far as I can tell.

[Sidney San Martín, 2016/09/14 18:34:37]

Ugh, I read that parameter as affecting position, but NSDivideRect isn't
responsible for that (and the position gets shifted on the next line). Fixed.

   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, 2016/09/14 18:06:37]

this top highlight code looks pretty similar to the previous top stroke code --
i guess this will grow a IsModeMaterial() call eventually too.

(nothing to do here; just remarking to myself that i can see why the stroke code
was here before this cl, but i also see how having it only once in the
superclass makes sense as well)

[Sidney San Martín, 2016/09/14 18:34:37]

I'm starting the MD version now :). Hopefully this whole block can be removed in
not too long.

     }
   }
 }
 
 // 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