[runtime] Implement %_ToLength via ToLengthStub.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 51ea6aa71536ebfa28b31a2b42ed49235001b582..b53d52a3b3a1e15cc5ac67115d0159690bac3952 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -52,6 +52,7 @@ namespace internal {
   V(StubFailureTrampoline)                  \
   V(SubString)                              \
   V(ToNumber)                               \
+  V(ToLength)                               \
   V(ToString)                               \
   V(ToObject)                               \
   V(VectorStoreICTrampoline)                \
@@ -3076,6 +3077,15 @@ class ToNumberStub final : public PlatformCodeStub {
 };
 
 
+class ToLengthStub final : public PlatformCodeStub {
+ public:
+  explicit ToLengthStub(Isolate* isolate) : PlatformCodeStub(isolate) {}
+
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(ToLength);
+  DEFINE_PLATFORM_CODE_STUB(ToLength, PlatformCodeStub);
+};
+
+
 class ToStringStub final : public PlatformCodeStub {
  public:
   explicit ToStringStub(Isolate* isolate) : PlatformCodeStub(isolate) {}