[Color] Remove SkColor constants from Background class

In Background class, the default value for |color_| is not used in any
of the subclasses: either a subclass will override the color with
SetNativeControlColor(), or a subclass will not use |color_| at all. So
change the initial value to a placeholder color.

Also replace CreateStandardPanelBackground() with directly calling
CreateThemedSolidBackground() to make shell window to use themed colors
and to remove unnecessary wrapping function.

BUG=1059867

Change-Id: I97c6cf8943046453516ba93dc3b779eb6740d658
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102785
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753734}

content/shell/BUILD.gn

@@ -406,6 +406,7 @@ jumbo_static_library("content_shell_lib") {
         "browser/shell_web_contents_view_delegate_views.cc",
       ]
       deps += [
+        "//ui/native_theme",
         "//ui/resources",
         "//ui/views:test_support",
         "//ui/views/controls/webview",

content/shell/browser/shell_views.cc

@@ -21,6 +21,7 @@
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/events/event.h"
+#include "ui/native_theme/native_theme_color_id.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/button/md_text_button.h"
 #include "ui/views/controls/textfield/textfield.h"
@@ -117,7 +118,8 @@ class ShellWindowDelegateView : public views::WidgetDelegateView,
  private:
   // Initialize the UI control contained in shell window
   void InitShellWindow() {
-    SetBackground(views::CreateStandardPanelBackground());
+    SetBackground(CreateThemedSolidBackground(
+        this, ui::NativeTheme::kColorId_WindowBackground));
 
     auto contents_view = std::make_unique<views::View>();
     auto toolbar_view = std::make_unique<views::View>();

ui/views/background.cc

@@ -12,8 +12,8 @@
 #include "build/build_config.h"
 #include "cc/paint/paint_flags.h"
 #include "ui/gfx/canvas.h"
-#include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
+#include "ui/native_theme/native_theme_color_id.h"
 #include "ui/views/painter.h"
 #include "ui/views/view.h"
 #include "ui/views/view_observer.h"
@@ -108,7 +108,7 @@ class BackgroundPainter : public Background {
   DISALLOW_COPY_AND_ASSIGN(BackgroundPainter);
 };
 
-Background::Background() : color_(SK_ColorWHITE) {}
+Background::Background() = default;
 
 Background::~Background() = default;
 
@@ -131,11 +131,6 @@ std::unique_ptr<Background> CreateThemedSolidBackground(
   return std::make_unique<ThemedSolidBackground>(view, color_id);
 }
 
-std::unique_ptr<Background> CreateStandardPanelBackground() {
-  // TODO(beng): Should be in NativeTheme.
-  return CreateSolidBackground(SK_ColorWHITE);
-}
-
 std::unique_ptr<Background> CreateBackgroundFromPainter(
     std::unique_ptr<Painter> painter) {
   return std::make_unique<BackgroundPainter>(std::move(painter));

ui/views/background.h

@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "ui/gfx/color_palette.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/views_export.h"
 
@@ -59,7 +60,7 @@ class VIEWS_EXPORT Background {
   SkColor get_color() const { return color_; }
 
  private:
-  SkColor color_;
+  SkColor color_ = gfx::kPlaceholderColor;
 
   DISALLOW_COPY_AND_ASSIGN(Background);
 };
@@ -78,9 +79,6 @@ VIEWS_EXPORT std::unique_ptr<Background> CreateThemedSolidBackground(
     View* view,
     ui::NativeTheme::ColorId color_id);
 
-// Creates Chrome's standard panel background
-VIEWS_EXPORT std::unique_ptr<Background> CreateStandardPanelBackground();
-
 // Creates a Background from the specified Painter.
 VIEWS_EXPORT std::unique_ptr<Background> CreateBackgroundFromPainter(
     std::unique_ptr<Painter> painter);

weblayer/shell/BUILD.gn

@@ -94,6 +94,7 @@ static_library("weblayer_shell_lib") {
     if (toolkit_views) {
       sources += [ "browser/shell_views.cc" ]
       deps += [
+        "//ui/native_theme",
         "//ui/resources",
         "//ui/views:test_support",
         "//ui/views/controls/webview",

weblayer/shell/DEPS

@@ -4,6 +4,7 @@ include_rules = [
   "+ui/base",
   "+ui/events",
   "+ui/gfx",
+  "+ui/native_theme",
   "+ui/views",
   "+ui/wm",
 ]

weblayer/shell/browser/shell_views.cc

@@ -17,6 +17,7 @@
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/events/event.h"
+#include "ui/native_theme/native_theme_color_id.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/button/md_text_button.h"
 #include "ui/views/controls/textfield/textfield.h"
@@ -107,7 +108,8 @@ class ShellWindowDelegateView : public views::WidgetDelegateView,
  private:
   // Initialize the UI control contained in shell window
   void InitShellWindow() {
-    SetBackground(views::CreateStandardPanelBackground());
+    SetBackground(CreateThemedSolidBackground(
+        this, ui::NativeTheme::kColorId_WindowBackground));
 
     auto contents_view = std::make_unique<views::View>();
     auto toolbar_view = std::make_unique<views::View>();