[es6] Tail calls support.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 35671d2c4c813c5adccd36ca989e9f101e6cb092..3889304f5c5b2d7cb5b5627a7d1b2c416643097f 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -3526,6 +3526,35 @@ Handle<Code> Builtins::Call(ConvertReceiverMode mode) {
 }
 
 
+Handle<Code> Builtins::TailCallFunction(ConvertReceiverMode mode) {
+  switch (mode) {
+    case ConvertReceiverMode::kNullOrUndefined:
+      return TailCallFunction_ReceiverIsNullOrUndefined();
+    case ConvertReceiverMode::kNotNullOrUndefined:
+      return TailCallFunction_ReceiverIsNotNullOrUndefined();
+    case ConvertReceiverMode::kAny:
+      return TailCallFunction_ReceiverIsAny();
+  }
+  UNREACHABLE();
+  return Handle<Code>::null();
+}
+
+
+Handle<Code> Builtins::TailCall(ConvertReceiverMode mode) {
+  UNREACHABLE();
+  switch (mode) {
+    case ConvertReceiverMode::kNullOrUndefined:
+      return Call_ReceiverIsNullOrUndefined();
+    case ConvertReceiverMode::kNotNullOrUndefined:
+      return Call_ReceiverIsNotNullOrUndefined();
+    case ConvertReceiverMode::kAny:
+      return Call_ReceiverIsAny();
+  }
+  UNREACHABLE();
+  return Handle<Code>::null();
+}
+
+
 namespace {
 
 class RelocatableArguments