Set callback interface on WebCDMSessionImpl after creation.

content/renderer/media/webcontentdecryptionmodulesession_impl.cc

Index: content/renderer/media/webcontentdecryptionmodulesession_impl.cc
diff --git a/content/renderer/media/webcontentdecryptionmodulesession_impl.cc b/content/renderer/media/webcontentdecryptionmodulesession_impl.cc
index c16ca9cd68ff954a409ac01eaf67be477170333b..f0f43beb81dfdd3b0ef10e8506623b055101a1c3 100644
--- a/content/renderer/media/webcontentdecryptionmodulesession_impl.cc
+++ b/content/renderer/media/webcontentdecryptionmodulesession_impl.cc
@@ -46,10 +46,8 @@ static blink::WebContentDecryptionModuleException ConvertException(
 }
 
 WebContentDecryptionModuleSessionImpl::WebContentDecryptionModuleSessionImpl(
-    Client* client,
     const scoped_refptr<CdmSessionAdapter>& adapter)
     : adapter_(adapter),
-      client_(client),
       is_closed_(false),
       next_available_result_index_(1),
       weak_ptr_factory_(this) {
@@ -75,6 +73,10 @@ WebContentDecryptionModuleSessionImpl::
   outstanding_results_.clear();
 }
 
+void WebContentDecryptionModuleSessionImpl::setClientInterface(Client* client) {
+  client_ = client;
+}
+
 blink::WebString WebContentDecryptionModuleSessionImpl::sessionId() const {
   return blink::WebString::fromUTF8(web_session_id_);
 }