bpf_dsl: fix argument-dependent lookup of BoolExpr operators

Review URL: https://codereview.chromium.org/543333002

Cr-Commit-Position: refs/heads/master@{#294127}

components/nacl/loader/nonsfi/nonsfi_sandbox.cc

@@ -43,11 +43,6 @@ using sandbox::bpf_dsl::Error;
 using sandbox::bpf_dsl::If;
 using sandbox::bpf_dsl::ResultExpr;
 
-// TODO(mdempsky): Make BoolExpr a standalone class so these operators can
-// be resolved via argument-dependent lookup.
-using sandbox::bpf_dsl::operator&&;
-using sandbox::bpf_dsl::operator||;
-
 namespace nacl {
 namespace nonsfi {
 namespace {

sandbox/linux/bpf_dsl/bpf_dsl.h

@@ -263,6 +263,14 @@ class SANDBOX_EXPORT Caser {
 // templates.
 namespace internal {
 
+// Make argument-dependent lookup work.  This is necessary because although
+// BoolExpr is defined in bpf_dsl, since it's merely a typedef for
+// scoped_refptr<const internal::BoolExplImpl>, argument-dependent lookup only
+// searches the "internal" nested namespace.
+using bpf_dsl::operator!;
+using bpf_dsl::operator||;
+using bpf_dsl::operator&&;
+
 // Returns a boolean expression that represents whether system call
 // argument |num| of size |size| is equal to |val|, when masked
 // according to |mask|.  Users should use the Arg template class below

sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.cc

@@ -88,11 +88,6 @@ using sandbox::bpf_dsl::Error;
 using sandbox::bpf_dsl::If;
 using sandbox::bpf_dsl::ResultExpr;
 
-// TODO(mdempsky): Make BoolExpr a standalone class so these operators can
-// be resolved via argument-dependent lookup.
-using sandbox::bpf_dsl::operator||;
-using sandbox::bpf_dsl::operator&&;
-
 namespace sandbox {
 
 // Allow Glibc's and Android pthread creation flags, crash on any other