media: Fix EncryptedMediaTest.UnknownKeySystemThrowsException on Mac ARM64

A binder for interface media.mojom.CdmInfobarService for the frame scope
was only registered at the chrome/ layer, but not in the content layer.
So when running content_browsertests, the render process was terminated
for bad Mojo message.

This CL fixes the issue by using an EmptyBinderForFrame for the service
at content layer.

Bug: 1128445
Change-Id: I5ce49b2af3a17035bad71b165bc8c24a0bd1b9e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441292
Auto-Submit: Xiaohan Wang <xhwang@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812562}

content/browser/browser_interface_binders.cc

@@ -153,6 +153,10 @@
 #include "third_party/blink/public/mojom/input/text_input_host.mojom.h"
 #endif
 
+#if defined(OS_MAC) && defined(ARCH_CPU_ARM_FAMILY)
+#include "media/mojo/mojom/cdm_infobar_service.mojom.h"
+#endif
+
 namespace content {
 namespace internal {
 
@@ -825,6 +829,11 @@ void PopulateBinderMapWithContext(
   map->Add<blink::mojom::RawClipboardHost>(
       base::BindRepeating(&RawClipboardHostImpl::Create));
 
+#if defined(OS_MAC) && defined(ARCH_CPU_ARM_FAMILY)
+  map->Add<media::mojom::CdmInfobarService>(base::BindRepeating(
+      &EmptyBinderForFrame<media::mojom::CdmInfobarService>));
+#endif
+
   GetContentClient()->browser()->RegisterBrowserInterfaceBindersForFrame(host,
                                                                          map);
 }