Should not expose proto headers in public SDK headers and not include absl

mutex.h in public SDK headers.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=249330673

media_cas_proxy_sdk/external/common/wvpl/wvpl_cas_proxy_session.h

@@ -13,7 +13,6 @@
 #include <string>
 #include <vector>
 
-#include "absl/synchronization/mutex.h"
 #include "sdk/external/common/wvpl/wvpl_sdk_session.h"
 
 namespace widevine {
@@ -107,9 +106,6 @@ class WvPLCASProxySession : public WvPLSDKSession {
 
   // holds all the WvPLCasKey objects.  Used when generating a CAS License.
   std::vector<WvPLCasKey> cas_keys_;
-
-  // Mutex to protect the keys, |cas_keys_|, owned by this session.
-  mutable std::unique_ptr<absl::Mutex> cas_keys_mutex_;
 };
 
 }  // namespace wv_pl_sdk

sdk/external/common/wvpl/wvpl_sdk_environment.h

@@ -13,7 +13,6 @@
 #include <string>
 
 #include "sdk/external/common/wvpl/wvpl_types.h"
-#include "protos/public/drm_certificate.pb.h"
 
 namespace widevine {
 class DeviceCertificateStatusList;
@@ -111,8 +110,7 @@ class WvPLSDKEnvironment {
 
  private:
   // Get the expected service type for drm service certificate.
-  virtual widevine::DrmCertificate::ServiceType
-  GetExpectedServiceCertificateType();
+  virtual int GetExpectedServiceCertificateType();
 
   // Check the type of |service_certificate|. Returns "OK" if the cert can be
   // used for the current SDK, else an error status.