Detect when unable to meet policy requirements

[ Merged of http://go/wvgerrit/39766 ]

The security level (software/hardware, decryption/decode)
in the policy that specified how the key was to be used was
not being respected for L3. Playback would either continue or
a vendor specific error would be thrown.

If the device cannot use the key as permitted by the policy
CryptoException#ERROR_INSUFFICIENT_OUTPUT_PROTECTION will be thrown.

Bug: 31913737
Bug: 31913439

Test: WV unit/integration tests
Test: Playback using playmovies and netflix. Cast playback using
      playmovies.

Change-Id: If25735ab0f789108431115623cb236687c5ef818

libwvdrmengine/cdm/core/include/policy_engine.h

@@ -39,6 +39,10 @@ class PolicyEngine {
   // out why a key is not usable.
   virtual CdmKeyStatus GetKeyStatus(const KeyId& key_id);
 
+  // Verifies whether the policy allows use of the specified key of
+  // a given security level for content decryption.
+  virtual bool CanUseKey(const KeyId& key_id, CdmSecurityLevel security_level);
+
   // OnTimerEvent is called when a timer fires. It notifies the Policy Engine
   // that the timer has fired and dispatches the relevant events through
   // |event_listener_|.