aw: Check for HasActiveFrame before getting frame

WebView/GLRenderer checks active frame of child surface for backdrop
filters to decide if merging SurfaceQuad is possible. If surface doesn't
have active frame it will fail CHECK.

This CL adds guard if the surface has active frame before retrieving to
prevent crashing.

Bug: 1100340
Change-Id: Ia02cead1c2195ba738ad19cf99db83b10669c948
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2300323Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788751}

android_webview/browser/gfx/surfaces_instance.cc

@@ -290,6 +290,10 @@ bool SurfacesInstance::BackdropFiltersPreventMerge(
   //  in the cases listed above. crbug.com/996434
   const viz::Surface* surface =
       frame_sink_manager_->surface_manager()->GetSurfaceForId(surface_id);
+
+  if (!surface || !surface->HasActiveFrame())
+    return false;
+
   const auto& frame = surface->GetActiveFrame();
   base::flat_set<viz::RenderPassId> backdrop_filter_passes;
   for (const auto& render_pass : frame.render_pass_list) {