[runtime] Ensure {JSGeneratorObject} is created for bytecode.

This removes some outdated code that allocates a {JSGeneratorObject} for
baseline code. We no longer support such a representation of generators
and can rely on bytecode being available for all generators.

R=neis@chromium.org

Review-Url: https://codereview.chromium.org/2515253003
Cr-Commit-Position: refs/heads/master@{#41137}

src/runtime/runtime-generator.cc

@@ -19,17 +19,11 @@ RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
   CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 1);
   CHECK(IsResumableFunction(function->shared()->kind()));
 
-  Handle<FixedArray> operand_stack;
-  if (function->shared()->HasBytecodeArray()) {
-    // New-style generators.
+  // Underlying function needs to have bytecode available.
+  DCHECK(function->shared()->HasBytecodeArray());
   DCHECK(!function->shared()->HasBaselineCode());
   int size = function->shared()->bytecode_array()->register_count();
-    operand_stack = isolate->factory()->NewFixedArray(size);
-  } else {
-    // Old-style generators.
-    DCHECK(function->shared()->HasBaselineCode());
-    operand_stack = isolate->factory()->empty_fixed_array();
-  }
+  Handle<FixedArray> operand_stack = isolate->factory()->NewFixedArray(size);
 
   Handle<JSGeneratorObject> generator =
       isolate->factory()->NewJSGeneratorObject(function);