Reset crypto session pointers on RemoveKeys.

[ Merge of http://go/wvgerrit/189650 ]

The CDM session shares its CryptoSession instance with a few additional
member objects (CdmLicense and PolicyEngine).  When the CDM session's
crypto session is reset, it must also reset the CdmLicense and
PolicyEngine otherwise, a potential stale pointer reference may occur.

Test: request_license_test on Oriole
Test: WVTS on Oriole
Bug: 311239278
Change-Id: Ie175513ae652dcd96e12e5e1def574a8a56d5863

libwvdrmengine/cdm/core/src/license.cpp

@@ -195,9 +195,7 @@ std::vector<CryptoKey> ExtractContentKeys(const License& license) {
 }  // namespace
 
 CdmLicense::CdmLicense(const CdmSessionId& session_id)
-    : crypto_session_(nullptr),
-      policy_engine_(nullptr),
-      session_id_(session_id),
+    : session_id_(session_id),
       initialized_(false),
       renew_with_client_id_(false),
       is_offline_(false),
@@ -206,15 +204,17 @@ CdmLicense::CdmLicense(const CdmSessionId& session_id)
       license_key_type_(kLicenseKeyTypeContent) {}
 
 CdmLicense::CdmLicense(const CdmSessionId& session_id, wvutil::Clock* clock)
-    : crypto_session_(nullptr),
-      policy_engine_(nullptr),
-      session_id_(session_id),
+    : session_id_(session_id),
       initialized_(false),
       renew_with_client_id_(false),
       is_offline_(false),
       use_privacy_mode_(false),
+      clock_(clock),
       license_key_type_(kLicenseKeyTypeContent) {
-  clock_.reset(clock);
+  if (!clock_) {
+    LOGW("Input |clock| is null, using default");
+    clock_.reset(new wvutil::Clock());
+  }
 }
 
 CdmLicense::~CdmLicense() {}