Decouple key fetcher; Update ECMG API

protos/public/media_cas_encryption.proto

@@ -0,0 +1,74 @@
+////////////////////////////////////////////////////////////////////////////////
+// Copyright 2018 Google LLC.
+//
+// This software is licensed under the terms defined in the Widevine Master
+// License Agreement. For a copy of this agreement, please contact
+// widevine-licensing@google.com.
+////////////////////////////////////////////////////////////////////////////////
+
+// Protocol buffer definitions for Widevine CAS.
+
+syntax = "proto2";
+
+package widevine;
+
+option java_package = "com.google.video.widevine.mediacasencryption";
+
+message CasEncryptionRequest {
+  optional bytes content_id = 1;
+  optional string provider = 2;
+  // Optional track types such as "AUDIO", SD" or "HD".
+  repeated string track_types = 3;
+  // Indicates if the client is using key rotation.  If true, the server will
+  // return one key for EVEN and one key for ODD, otherwise only a single key is
+  // returned.
+  optional bool key_rotation = 4;
+}
+
+message CasEncryptionResponse {
+  enum Status {
+    STATUS_UNSPECIFIED = 0;
+    OK = 1;
+    SIGNATURE_FAILED = 2;
+    ACCESS_DENIED = 3;
+    INTERNAL_ERROR = 4;
+    INVALID_ARGUMENT = 5;
+    PROVIDER_ID_MISSING = 6;
+    CONTENT_ID_MISSING = 7;
+    TRACK_TYPE_MISSING = 8;
+  }
+  message KeyInfo {
+    enum KeySlot {
+      KEY_SLOT_UNSPECIFIED = 0;
+      SINGLE = 1;
+      EVEN = 2;
+      ODD = 3;
+    }
+    optional bytes key_id = 1;
+    optional bytes key = 2;
+    // Optional label used for the key.
+    optional string track_type = 3;
+    optional KeySlot key_slot = 4;
+  }
+  optional Status status = 1;
+  optional string status_message = 2;
+  optional bytes content_id = 3;
+  repeated KeyInfo entitlement_keys = 4;
+}
+
+message SignedCasEncryptionRequest {
+  optional bytes request = 1;
+  optional bytes signature = 2;
+  // Identifies the entity sending / signing the request.
+  optional string signer = 3;
+}
+
+message SignedCasEncryptionResponse {
+  // Serialized CasEncryptionResponse message.
+  optional bytes response = 1;
+  optional bytes signature = 2;
+}
+
+message HttpResponse {
+  optional bytes response = 1;
+}