Rename CancelKeyRequest

(This is a merge of http://go/wvgerrit/10674 from the Widevine CDM
repository.)

Now that the CE CDM has CloseSession to handle closing sessions, we
can rename CancelKeyRequest on the CDM Engine & CDM Session to better
resemble its purpose and the name it is known by on Android.

Change-Id: I68d55b3be733579e5875ab33d8e94a62fe1f651d

libwvdrmengine/cdm/include/wv_content_decryption_module.h

@@ -53,7 +53,7 @@ class WvContentDecryptionModule : public TimerHandler {
                                      const CdmKeySetId& key_set_id);
 
   // Cancel session
-  virtual CdmResponseType CancelKeyRequest(const CdmSessionId& session_id);
+  virtual CdmResponseType RemoveKeys(const CdmSessionId& session_id);
 
   // Query system information
   virtual CdmResponseType QueryStatus(CdmQueryMap* key_info);