Add basic video support to mojo html_viewer

mojo/services/html_viewer/webmimeregistry_impl.cc

Index: mojo/services/html_viewer/webmimeregistry_impl.cc
diff --git a/mojo/services/html_viewer/webmimeregistry_impl.cc b/mojo/services/html_viewer/webmimeregistry_impl.cc
index edaed24e39e9cdfb0161e7a34e4aaec720ff2bf0..2faac176dedb38022cd271d0bb910ba795c61754 100644
--- a/mojo/services/html_viewer/webmimeregistry_impl.cc
+++ b/mojo/services/html_viewer/webmimeregistry_impl.cc
@@ -58,8 +58,32 @@ blink::WebMimeRegistry::SupportsType WebMimeRegistryImpl::supportsMediaMIMEType(
     const blink::WebString& mime_type,
     const blink::WebString& codecs,
     const blink::WebString& key_system) {
-  NOTIMPLEMENTED();
-  return IsNotSupported;
+  const std::string mime_type_ascii = ToASCIIOrEmpty(mime_type);
+  // Not supporting the container is a flat-out no.
+  if (!net::IsSupportedMediaMimeType(mime_type_ascii))
+    return IsNotSupported;
+
+  // Mojo does not currently support any key systems.
+  if (!key_system.isEmpty())
+    return IsNotSupported;
+
+  // Check list of strict codecs to see if it is supported.
+  if (net::IsStrictMediaMimeType(mime_type_ascii)) {
+    // Check if the codecs are a perfect match.
+    std::vector<std::string> strict_codecs;
+    net::ParseCodecString(ToASCIIOrEmpty(codecs), &strict_codecs, false);
+    return static_cast<WebMimeRegistry::SupportsType>(
+        net::IsSupportedStrictMediaMimeType(mime_type_ascii, strict_codecs));
+  }
+
+  // If we don't recognize the codec, it's possible we support it.
+  std::vector<std::string> parsed_codecs;
+  net::ParseCodecString(ToASCIIOrEmpty(codecs), &parsed_codecs, true);
+  if (!net::AreSupportedMediaCodecs(parsed_codecs))
+    return MayBeSupported;
+
+  // Otherwise we have a perfect match.
+  return IsSupported;
 }
 
 bool WebMimeRegistryImpl::supportsMediaSourceMIMEType(