Speculative fix for InstallableUtils crash

The WebAppProvider can be uninitialized. Dependencies should use the
on_registry_ready() signal. This change is a quick & mergeable fix for
a related crash, after which the codepaths will be turned async if
possible.

TBR-ing dominick so this change can get a canary roll, and they can
look at it when they get in on Monday. Patch is very low-risk -
resolving crash when there used to be a crash.

R=pwnall@chromium.org

TBR: dominickn@chromium.org
Bug: 1129921
Change-Id: I57c6d4f181f28c178df85c60626423a5619f9494
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2419537
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808617}

chrome/browser/installable/installable_utils.cc

@@ -41,6 +41,10 @@ bool DoesOriginContainAnyInstalledWebApp(
 #else
   auto* provider = web_app::WebAppProviderFactory::GetForProfile(
       Profile::FromBrowserContext(browser_context));
+  // TODO: Change this method to async, or document that the caller must know
+  // that WebAppProvider is started.
+  if (!provider || !provider->on_registry_ready().is_signaled())
+    return false;
   return provider->registrar().DoesScopeContainAnyApp(origin);
 #endif
 }
@@ -50,9 +54,13 @@ std::set<GURL> GetOriginsWithInstalledWebApps(
 #if defined(OS_ANDROID)
   return ShortcutHelper::GetOriginsWithInstalledWebApksOrTwas();
 #else
-  const web_app::AppRegistrar& registrar =
-      web_app::WebAppProvider::Get(Profile::FromBrowserContext(browser_context))
-          ->registrar();
+  auto* provider = web_app::WebAppProvider::Get(
+      Profile::FromBrowserContext(browser_context));
+  // TODO: Change this method to async, or document that the caller must know
+  // that WebAppProvider is started.
+  if (!provider || !provider->on_registry_ready().is_signaled())
+    return std::set<GURL>();
+  const web_app::AppRegistrar& registrar = provider->registrar();
   auto app_ids = registrar.GetAppIds();
   std::set<GURL> installed_origins;
   for (auto& app_id : app_ids) {