Refactor KeySystems code to call a function to populate the info. (relanding r221932)

content/public/renderer/content_renderer_client.cc

Index: content/public/renderer/content_renderer_client.cc
diff --git a/content/public/renderer/content_renderer_client.cc b/content/public/renderer/content_renderer_client.cc
index 50a911764008dc4b51c7e2e8e28979b834b2fcba..2621de3023e574cbc8cb4572ee9389a1ba75db1d 100644
--- a/content/public/renderer/content_renderer_client.cc
+++ b/content/public/renderer/content_renderer_client.cc
@@ -182,6 +182,10 @@ bool ContentRendererClient::AllowPepperMediaStreamAPI(const GURL& url) {
   return false;
 }
 
+void ContentRendererClient::AddKeySystems(
+    std::vector<KeySystemInfo>* key_systems) {
+}
+
 bool ContentRendererClient::ShouldReportDetailedMessageForSource(
     const base::string16& source) const {
   return false;