Allow inlining of functions containing %_ArgumentsLength.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 4e7b1a36ffebbe36a6ee8ad25224fb1d62f9d5c3..34b80828c0897851518335a5d4787e61a34116df 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -11310,13 +11310,17 @@ void HOptimizedGraphBuilder::GenerateIsConstructCall(CallRuntime* call) {
 
 // Support for arguments.length and arguments[?].
 void HOptimizedGraphBuilder::GenerateArgumentsLength(CallRuntime* call) {
-  // Our implementation of arguments (based on this stack frame or an
-  // adapter below it) does not work for inlined functions.  This runtime
-  // function is blacklisted by AstNode::IsInlineable.
-  ASSERT(function_state()->outer() == NULL);
   ASSERT(call->arguments()->length() == 0);
-  HInstruction* elements = Add<HArgumentsElements>(false);
-  HArgumentsLength* result = New<HArgumentsLength>(elements);
+  HInstruction* result = NULL;
+  if (function_state()->outer() == NULL) {
+    HInstruction* elements = Add<HArgumentsElements>(false);
+    result = New<HArgumentsLength>(elements);
+  } else {
+    // Number of arguments without receiver.
+    int argument_count = environment()->
+        arguments_environment()->parameter_count() - 1;
+    result = New<HConstant>(argument_count);
+  }
   return ast_context()->ReturnInstruction(result, call->id());
 }