[Web Payment] Check WebContents not null.

This patch checks the result of WebContents::FromRenderFrameHost() for
null to avoid crashing.

Bug: 1064628
Change-Id: Ib755a014e72e2428e8343aa2aac2b3b707c484ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2572908Reviewed-by: Liquan (Max) Gu <maxlg@chromium.org>
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833816}

components/payments/content/installable_payment_app_crawler.cc

@@ -427,7 +427,10 @@ bool InstallablePaymentAppCrawler::DownloadAndDecodeWebAppIcon(
   // TODO(crbug.com/1058840): Move this sanity check to ManifestIconDownloader
   // after DownloadImage refactor is done.
   auto* rfh = content::RenderFrameHost::FromID(initiator_frame_routing_id_);
-  if (!rfh || !rfh->IsCurrent()) {
+  auto* web_contents = rfh && rfh->IsCurrent()
+                           ? content::WebContents::FromRenderFrameHost(rfh)
+                           : nullptr;
+  if (!web_contents) {
     log_.Warn(
         "Cannot download icons after the webpage has been closed (web app "
         "manifest \"" +
@@ -442,7 +445,6 @@ bool InstallablePaymentAppCrawler::DownloadAndDecodeWebAppIcon(
     return false;
   }
 
-  auto* web_contents = content::WebContents::FromRenderFrameHost(rfh);
   gfx::NativeView native_view = web_contents->GetNativeView();
   GURL best_icon_url = blink::ManifestIconSelector::FindBestMatchingIcon(
       manifest_icons, IconSizeCalculator::IdealIconHeight(native_view),