Add a MathFloor stub generated with TurboFan

src/ia32/interface-descriptors-ia32.cc

Index: src/ia32/interface-descriptors-ia32.cc
diff --git a/src/ia32/interface-descriptors-ia32.cc b/src/ia32/interface-descriptors-ia32.cc
index fc5c5c393139c5c0f4402ec1880468e56b8ce905..edee490c7421b6992628b7780b195e3c14e56700 100644
--- a/src/ia32/interface-descriptors-ia32.cc
+++ b/src/ia32/interface-descriptors-ia32.cc
@@ -364,6 +364,21 @@ void ApiAccessorDescriptor::Initialize(CallInterfaceDescriptorData* data) {
   };
   data->Initialize(arraysize(registers), registers, representations);
 }
+
+
+void MathRoundVariantDescriptor::Initialize(CallInterfaceDescriptorData* data) {
+  Register registers[] = {
+      esi,  // context
+      edi,  // math rounding function
+      edx,  // vector slot id
+  };
+  Representation representations[] = {
+      Representation::Tagged(),  //
+      Representation::Tagged(),  //
+      Representation::Tagged(),  //
+  };
+  data->Initialize(arraysize(registers), registers, representations);
+}
 }
 }  // namespace v8::internal