[turbofan] Introduce an ExternalPointer type.

test/unittests/compiler/node-test-utils.cc

Index: test/unittests/compiler/node-test-utils.cc
diff --git a/test/unittests/compiler/node-test-utils.cc b/test/unittests/compiler/node-test-utils.cc
index eb737cb93c245f86d7113bdd03513f192e9f1b80..83526916443ec4380ebaf8cc95fd7245439ac1c8 100644
--- a/test/unittests/compiler/node-test-utils.cc
+++ b/test/unittests/compiler/node-test-utils.cc
@@ -1790,6 +1790,10 @@ Matcher<Node*> IsNumberConstant(const Matcher<double>& value_matcher) {
       new IsConstantMatcher<double>(IrOpcode::kNumberConstant, value_matcher));
 }
 
+Matcher<Node*> IsPointerConstant(const Matcher<intptr_t>& value_matcher) {
+  return MakeMatcher(new IsConstantMatcher<intptr_t>(IrOpcode::kPointerConstant,
+                                                     value_matcher));
+}
 
 Matcher<Node*> IsSelect(const Matcher<MachineRepresentation>& type_matcher,
                         const Matcher<Node*>& value0_matcher,