Show separator in SearchResultTileItemListView

ui/app_list/views/search_result_separator.cc

+// Copyright (c) 2017 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 "ui/app_list/views/search_result_separator.h"
+
+#include "ui/gfx/canvas.h"
+#include "ui/views/border.h"
+
+namespace {
+
+constexpr int kSeparatorLeftRightPadding = 4;
+constexpr int kSeparatorHeight = 36;
+constexpr SkColor kSeparatorColor = SkColorSetARGBMacro(0x1F, 0x00, 0x00, 0x00);
+
+}  // namespace
+
+namespace app_list {
+
+SearchResultSeparator::SearchResultSeparator() {

[xiyuan, 2017/06/23 15:43:09]

This class seems unnecessary. Can we achieve the same effect by using the
existing Separator class?

[weidongg, 2017/06/23 18:32:20]

Using Separator::SetPreferredHeight to set height does not seem to work. The
separator's height always matches the parent's height. Should I make change in
the Separator class to force the height to be preferred height?

[xiyuan, 2017/06/23 20:09:01]

Preferred height is just preferred and parent can choose to ignore it. For our
case here, we need need top/bottom padding. We can add that with the
CreateEmptyBorder call.

+  SetBorder(views::CreateEmptyBorder(0, kSeparatorLeftRightPadding, 0,
+                                     kSeparatorLeftRightPadding));
+}
+
+SearchResultSeparator::~SearchResultSeparator() {}
+
+void SearchResultSeparator::OnPaint(gfx::Canvas* canvas) {
+  gfx::Rect contents_bound = GetContentsBounds();
+  contents_bound.set_height(kSeparatorHeight);
+
+  float dsf = canvas->UndoDeviceScaleFactor();
+  gfx::RectF contents = gfx::ScaleRect(gfx::RectF(contents_bound), dsf);
+  canvas->FillRect(gfx::ToEnclosedRect(contents), kSeparatorColor);
+
+  View::OnPaint(canvas);
+}
+
+}  // namespace app_list