Replace scoped_ptr With std::unique_ptr

(This is a merge of http://go/wvgerrit/65782)

We have had our own scoped_ptr implementation that is used throughout
the codebase. Now that we support C++11, we can replace these with
std::unique_ptr.

Doing this replacement exposed a few places where the two were not
interchangeable. OEMCrypto Ref was doing some unsafe things with passing
scoped_ptrs to functions and has been updated to use move semantics. And
a few constructors were explicitly constructing a scoped_ptr with NULL,
which is ambiguous with std::unique_ptr. These have been replaced with
default constructor calls.

Bug: 111851141
Test: CE CDM Unit Tests
Test: Android Unit Tests
Change-Id: I37d6d7aad4906709381c74f0c5439f826d2be768

libwvdrmengine/oemcrypto/ref/src/oemcrypto_engine_ref.cpp

@@ -11,6 +11,7 @@
 #include <string.h>
 #include <algorithm>
 #include <iostream>
+#include <utility>
 #include <vector>
 
 #include <openssl/err.h>
@@ -27,10 +28,10 @@ namespace wvoec_ref {
 // all configurations.  See the files oemcrypto_engine_device_properties*.cpp
 // for methods that are configured for specific configurations.
 
-CryptoEngine::CryptoEngine(scoped_ptr<wvcdm::FileSystem> file_system)
+CryptoEngine::CryptoEngine(std::unique_ptr<wvcdm::FileSystem>&& file_system)
     : root_of_trust_(config_provisioning_method()),
-      file_system_(file_system),
-      usage_table_(NULL) {
+      file_system_(std::move(file_system)),
+      usage_table_() {
   ERR_load_crypto_strings();
 }