Allows sharing of keys between sessions

This change allows the app to specify that keys may be shared by sessions.
The app enables this by setting the session sharing properties in DRM Plugin.
Keys are shared only amoungst the specified group of sessions.

Merged from widevine CDM repo
 * https://widevine-internal-review.googlesource.com/#/c/8019/
 * https://widevine-internal-review.googlesource.com/#/c/8021/

Bug: 11013707
Change-Id: I52db41a53138b4fc563ebc6d38a623f23f7cdfb5

libwvdrmengine/cdm/core/include/cdm_client_property_set.h

@@ -16,6 +16,9 @@ class CdmClientPropertySet {
   virtual std::string security_level() const = 0;
   virtual bool use_privacy_mode() const = 0;
   virtual std::vector<uint8_t> service_certificate() const = 0;
+  virtual bool is_session_sharing_enabled() const = 0;
+  virtual uint32_t session_sharing_id() const = 0;
+  virtual void set_session_sharing_id(uint32_t id) = 0;
 };
 
 }  // namespace wvcdm

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -93,6 +93,7 @@ class CdmEngine : public TimerHandler {
 
   // Is the key known to any session?
   virtual bool IsKeyValid(const KeyId& key_id);
+  virtual bool FindSessionForKey(const KeyId& key_id, CdmSessionId* sessionId);
 
   // Event listener related methods
   virtual bool AttachEventListener(const CdmSessionId& session_id,

libwvdrmengine/cdm/core/include/license.h

@@ -3,6 +3,8 @@
 #ifndef CDM_BASE_LICENSE_H_
 #define CDM_BASE_LICENSE_H_
 
+#include <set>
+
 #include "wv_cdm_types.h"
 
 namespace video_widevine_server {
@@ -41,6 +43,7 @@ class CdmLicense {
                              CdmKeyResponse& license_response,
                              CdmKeyResponse& license_renewal_response);
   bool HasInitData() { return !init_data_.empty(); }
+  bool IsKeyLoaded(const KeyId& key_id);
 
  private:
   bool PrepareServiceCertificateRequest(CdmKeyMessage* signed_request,
@@ -58,6 +61,7 @@ class CdmLicense {
   std::string service_certificate_;
   std::string init_data_;
   bool initialized_;
+  std::set<KeyId> loaded_keys_;
 
   // Used for certificate based licensing
   CdmKeyMessage key_request_;

libwvdrmengine/cdm/core/include/properties.h

@@ -66,6 +66,7 @@ class Properties {
   static const std::vector<uint8_t> GetServiceCertificate(
        const CdmSessionId& session_id);
   static bool UsePrivacyMode(const CdmSessionId& session_id);
+  static uint32_t GetSessionSharingId(const CdmSessionId& session_id);
 
   static bool AddSessionPropertySet(
       const CdmSessionId& session_id,