DevTools: account for the display scale factor while validating manifest under emulation.

chrome/browser/banners/app_banner_manager_emulation.cc

+// Copyright 2016 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 "chrome/browser/banners/app_banner_manager_emulation.h"
+
+#include "base/command_line.h"
+#include "build/build_config.h"
+#include "chrome/browser/banners/app_banner_data_fetcher_desktop.h"
+#include "ui/display/screen.h"
+
+namespace {
+
+// We need to provide web developers with the guidance on the minimum icon
+// size they should list in the manifest. Since the size depends on the
+// device, we pick the baseline being a Nexus 5X-alike device.
+// We make it clear in the 'add to home screen' emulation UI that the
+// size does not correspond to the currently emulated device, but rather is
+// a generic baseline.
+const int kMinimumIconSize = 144;
+
+}  // anonymous namespace
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(banners::AppBannerManagerEmulation);
+
+namespace banners {
+
+AppBannerDataFetcher* AppBannerManagerEmulation::CreateAppBannerDataFetcher(
+    base::WeakPtr<AppBannerDataFetcher::Delegate> weak_delegate,
+    bool is_debug_mode) {
+
+  // Divide by the current screen density as the data fetcher will multiply
+  // it back in when trying to fetch an appropriate icon
+  int size = kMinimumIconSize / display::Screen::GetScreen()->
+      GetPrimaryDisplay().device_scale_factor();
+
+  return new AppBannerDataFetcherDesktop(web_contents(), weak_delegate,
+                                         size, size, is_debug_mode);
+}
+
+AppBannerManagerEmulation::AppBannerManagerEmulation(
+    content::WebContents* web_contents)
+    : AppBannerManager(web_contents) {
+}
+
+}  // namespace banners