[sheriff] Revert "Always use a white theme for System App popup settings pages"

This reverts commit 00abf52b.

Reason for revert: Failures on Mac ASan 64 Tests:
https://ci.chromium.org/p/chromium/builders/ci/Mac%20ASan%2064%20Tests%20%281%29/60954

Original change's description:
> Always use a white theme for System App popup settings pages
> 
> Bug: 1033339
> Change-Id: Ia8f0c24deb742d04b0a10bb4fbcb4c3322ea1547
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065776
> Commit-Queue: Joel Hockey <joelhockey@chromium.org>
> Reviewed-by: Alan Cutter <alancutter@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#742992}

TBR=alancutter@chromium.org,joelhockey@chromium.org

Change-Id: I6152c170c342622e8c53a5566e8b9d2488ebe1c6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1033339
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065005Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743047}

chrome/browser/ui/web_applications/app_browser_controller.cc

@@ -288,10 +288,6 @@ void AppBrowserController::DidChangeThemeColor() {
 }
 
 base::Optional<SkColor> AppBrowserController::GetThemeColor() const {
-  // System App popus (settings pages) always use white theme.
-  if (system_app_type_ && browser_->is_type_app_popup())
-    return SK_ColorWHITE;
-
   base::Optional<SkColor> result;
   // HTML meta theme-color tag overrides manifest theme_color, see spec:
   // https://www.w3.org/TR/appmanifest/#theme_color-member

chrome/browser/ui/web_applications/app_browser_controller_browsertest.cc

@@ -101,16 +101,6 @@ class AppBrowserControllerBrowserTest : public InProcessBrowserTest {
         tabbed_app_url_));
   }
 
-  void InstallAndLaunchMockPopup() {
-    test_system_web_app_installation_->WaitForAppInstall();
-    auto params = web_app::CreateSystemWebAppLaunchParams(
-        browser()->profile(), test_system_web_app_installation_->GetType());
-    params->disposition = WindowOpenDisposition::NEW_POPUP;
-    app_browser_ = web_app::LaunchSystemWebApp(
-        browser()->profile(), test_system_web_app_installation_->GetType(),
-        test_system_web_app_installation_->GetAppUrl(), *params);
-  }
-
   GURL GetActiveTabURL() {
     return app_browser_->tab_strip_model()
         ->GetActiveWebContents()
@@ -198,10 +188,4 @@ IN_PROC_BROWSER_TEST_F(AppBrowserControllerBrowserTest, TabLoadNoThemeChange) {
   EXPECT_EQ(GetTabColor(app_browser_), SK_ColorGREEN);
 }
 
-IN_PROC_BROWSER_TEST_F(AppBrowserControllerBrowserTest,
-                       WhiteThemeForSystemAppPopup) {
-  InstallAndLaunchMockPopup();
-  EXPECT_EQ(app_browser_->app_controller()->GetThemeColor(), SK_ColorWHITE);
-}
-
 }  // namespace web_app