Uniformly handle 'undefined' store to Float64Array and Float32Array.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 7bcccdf9fbf443424884f6f0b758c3e7a595c6a3..23f142e307ba0d87840e0888e25faf7d21da8029 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -11757,7 +11757,7 @@ MaybeObject* ExternalUnsignedIntArray::SetValue(uint32_t index, Object* value) {
 
 
 MaybeObject* ExternalFloatArray::SetValue(uint32_t index, Object* value) {
-  float cast_value = 0;
+  float cast_value = OS::nan_value();
   Heap* heap = GetHeap();
   if (index < static_cast<uint32_t>(length())) {
     if (value->IsSmi()) {
@@ -11778,7 +11778,7 @@ MaybeObject* ExternalFloatArray::SetValue(uint32_t index, Object* value) {
 
 
 MaybeObject* ExternalDoubleArray::SetValue(uint32_t index, Object* value) {
-  double double_value = 0;
+  double double_value = OS::nan_value();
   Heap* heap = GetHeap();
   if (index < static_cast<uint32_t>(length())) {
     if (value->IsSmi()) {