Remove usage reports upon factory reset of device.

(This is a merge of http://go/wvgerrit/16162)

Usage tables on L3 devices are stored under IDM*. They will be removed
upon factory reset. However, we need to call OEMCrypto_DeleteUsageTable
for L1 devices because the usage tables are stored in secure storage.

bug: 25597957
Change-Id: I8533dfac60fad6ce7ddfd026a283633d6875dcf3

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -173,6 +173,7 @@ class CdmEngine {
 
  private:
   // private methods
+  void DeleteAllUsageReportsUponFactoryReset();
   bool ValidateKeySystem(const CdmKeySystem& key_system);
   CdmResponseType GetUsageInfo(const std::string& app_id,
                                SecurityLevel requested_security_level,