[compiler] Introduce StringEqualStub and StringNotEqualStub.

src/compiler/code-stub-assembler.cc

Index: src/compiler/code-stub-assembler.cc
diff --git a/src/compiler/code-stub-assembler.cc b/src/compiler/code-stub-assembler.cc
index b340c10d89b4eeb5ffbe5b6d483e4474a2e41ef3..0813cbed91029a093e77a173e27ea5033c339a29 100644
--- a/src/compiler/code-stub-assembler.cc
+++ b/src/compiler/code-stub-assembler.cc
@@ -602,6 +602,14 @@ Node* CodeStubAssembler::CallStub(const CallInterfaceDescriptor& descriptor,
   return CallN(call_descriptor, target, args);
 }
 
+Node* CodeStubAssembler::TailCallStub(Callable const& callable, Node* context,
+                                      Node* arg1, Node* arg2,
+                                      size_t result_size) {
+  Node* target = HeapConstant(callable.code());
+  return TailCallStub(callable.descriptor(), target, context, arg1, arg2,
+                      result_size);
+}
+
 Node* CodeStubAssembler::TailCallStub(const CallInterfaceDescriptor& descriptor,
                                       Node* target, Node* context, Node* arg1,
                                       Node* arg2, size_t result_size) {