Make TrustStore into an interface, move impl to TrustStoreInMemory.

components/cast_certificate/cast_cert_validator.cc

Index: components/cast_certificate/cast_cert_validator.cc
diff --git a/components/cast_certificate/cast_cert_validator.cc b/components/cast_certificate/cast_cert_validator.cc
index 3e9bb222a2663bc9fb0fc8a33098d4826faaa013..975894c75c8de264d69ac9087b2d08e39d54db99 100644
--- a/components/cast_certificate/cast_cert_validator.cc
+++ b/components/cast_certificate/cast_cert_validator.cc
@@ -23,7 +23,7 @@
 #include "net/cert/internal/path_builder.h"
 #include "net/cert/internal/signature_algorithm.h"
 #include "net/cert/internal/signature_policy.h"
-#include "net/cert/internal/trust_store.h"
+#include "net/cert/internal/trust_store_static.h"
 #include "net/cert/internal/verify_signed_data.h"
 #include "net/der/encode_values.h"
 #include "net/der/input.h"
@@ -79,7 +79,7 @@ class CastTrustStore {
     store_.AddTrustAnchor(std::move(anchor));
   }
 
-  net::TrustStore store_;
+  net::TrustStoreStatic store_;
   DISALLOW_COPY_AND_ASSIGN(CastTrustStore);
 };