Store key set ID with usage info

[ Merge of http://go/wvgerrit/16241 and http://go/wvgerrit/16364 ]

This will allow a usage session to be loaded later by key set ID.
This is needed for EME-style secure stop in the new CE CDM API.

b/25816911

Change-Id: I916340047492fbc0556d0e90bd2eac0f3eafe597

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -146,6 +146,8 @@ class CdmEngine {
   virtual CdmResponseType ReleaseAllUsageInfo(const std::string& app_id);
   virtual CdmResponseType ReleaseUsageInfo(
       const CdmUsageInfoReleaseMessage& message);
+  virtual CdmResponseType LoadUsageSession(const CdmKeySetId& key_set_id,
+                                           CdmKeyMessage* release_message);
 
   // Decryption and key related methods
   // Accept encrypted buffer and return decrypted data.

libwvdrmengine/cdm/core/include/device_files.h

@@ -72,7 +72,8 @@ class DeviceFiles {
   virtual bool StoreUsageInfo(const std::string& provider_session_token,
                               const CdmKeyMessage& key_request,
                               const CdmKeyResponse& key_response,
-                              const std::string& app_id);
+                              const std::string& app_id,
+                              const std::string& key_set_id);
   virtual bool DeleteUsageInfo(const std::string& app_id,
                                const std::string& provider_session_token);
   // Delete usage information from the file system.  Puts a list of all the
@@ -91,6 +92,12 @@ class DeviceFiles {
                                  const std::string& provider_session_token,
                                  CdmKeyMessage* license_request,
                                  CdmKeyResponse* license_response);
+  // Retrieve the usage info entry specified by |key_set_id|.
+  // Returns false if the entry could not be found.
+  virtual bool RetrieveUsageInfoByKeySetId(const std::string& app_id,
+                                           const std::string& key_set_id,
+                                           CdmKeyMessage* license_request,
+                                           CdmKeyResponse* license_response);
 
  private:
   // Helpers that wrap the File interface and automatically handle hashing, as