[builtins] Introduce proper Float64Atan and Float64Atan2 operators.

src/external-reference-table.cc

Index: src/external-reference-table.cc
diff --git a/src/external-reference-table.cc b/src/external-reference-table.cc
index 0a595386022115e0830617b7cac941e753a936fc..d0aa08849b1a9127198f38f7efe8eaba2f5070db 100644
--- a/src/external-reference-table.cc
+++ b/src/external-reference-table.cc
@@ -67,6 +67,10 @@ ExternalReferenceTable::ExternalReferenceTable(Isolate* isolate) {
       "power_double_double_function");
   Add(ExternalReference::power_double_int_function(isolate).address(),
       "power_double_int_function");
+  Add(ExternalReference::ieee754_atan_function(isolate).address(),
+      "base::ieee754::atan");
+  Add(ExternalReference::ieee754_atan2_function(isolate).address(),
+      "base::ieee754::atan2");
   Add(ExternalReference::ieee754_log_function(isolate).address(),
       "base::ieee754::log");
   Add(ExternalReference::ieee754_log1p_function(isolate).address(),