DPWA: switch to DCHECK icon_manager_ for GetShortcutInfoForApp

CHECK was added to investigate crash reports related to
GetShortcutInfoForApp, based on ongoing investigation, the crash is caused
at line 53 for getting icon_sizes_in_px, likely due to null app.
Therefore removing this CHECK.

Bug: 1113276
Change-Id: I661d80cc29476e6b15fb29348928664f70cf8121
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2388946Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Phillis Tang <phillis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803682}

chrome/browser/web_applications/web_app_shortcut_manager.cc

@@ -54,9 +54,7 @@ void WebAppShortcutManager::GetShortcutInfoForApp(
       app->downloaded_icon_sizes(IconPurpose::ANY),
       GetDesiredIconSizesForShortcut());
 
-  // Optimistic check to help debug low-frequency crash.
-  // TODO(crbug.com/1113276): Make this a DCHECK before hitting stable.
-  CHECK(icon_manager_);
+  DCHECK(icon_manager_);
   if (!icon_sizes_in_px.empty()) {
     icon_manager_->ReadIcons(app_id, IconPurpose::ANY, icon_sizes_in_px,
                              base::BindOnce(&WebAppShortcutManager::OnIconsRead,