Revert "Use mediadrm from private instead of tangorpro"

Revert submission 29489024-pixel_tablet_mediadrm

Reason for revert: DroidMonitor: Potential culprit for http://b/369192150 - Verifying through ABTD before submission. 

Reverted changes: /q/submissionid:29489024-pixel_tablet_mediadrm

Change-Id: I3c1c31b871275bf2b5ceb93120918f749f828cd1

cast_auth/mediadrm/SessionLibrary.cpp

@@ -0,0 +1,39 @@
+#include "SessionLibrary.h"
+
+#include <algorithm>
+#include <string>
+
+namespace castkeydrm {
+
+std::mutex SessionLibrary::singleton_lock_;
+SessionLibrary* SessionLibrary::singleton_ = NULL;
+
+SessionLibrary* SessionLibrary::get() {
+    std::lock_guard<std::mutex> guard(singleton_lock_);
+
+    if (singleton_ == NULL) {
+        singleton_ = new SessionLibrary();
+    }
+
+    return singleton_;
+}
+
+std::vector<uint8_t> SessionLibrary::createSession() {
+    std::lock_guard<std::mutex> guard(session_lock_);
+
+    std::string session_string = std::to_string(next_session_id_);
+    next_session_id_ += 1;
+    sessions_.emplace_back(session_string.begin(), session_string.end());
+    return sessions_.back();
+}
+
+void SessionLibrary::closeSession(const std::vector<uint8_t>& session) {
+    std::lock_guard<std::mutex> guard(session_lock_);
+    sessions_.erase(std::remove_if(sessions_.begin(), sessions_.end(),
+                                   [&session](const std::vector<uint8_t>& e) {
+                                     return std::equal(e.begin(), e.end(), session.begin());
+                                   }),
+                    sessions_.end());
+}
+
+} // namespace castkeydrm