fix Error.captureStackTrace is undef error on browsers

errors.js

@@ -15,6 +15,12 @@ function getValue (value) {
   return value
 }
 
+function captureStackTrace (e, t) {
+  if (Error.captureStackTrace) {
+    Error.captureStackTrace(e, t)
+  }
+}
+
 function tfJSON (type) {
   if (native.Function(type)) return type.toJSON ? type.toJSON() : getTypeName(type)
   if (native.Array(type)) return 'Array'
@@ -35,7 +41,7 @@ function TfTypeError (type, value, valueTypeName) {
   valueTypeName = valueTypeName || getValueTypeName(value)
   this.message = tfErrorString(type, value, valueTypeName)
 
-  Error.captureStackTrace(this, TfTypeError)
+  captureStackTrace(this, TfTypeError)
   this.__type = type
   this.__value = value
   this.__valueTypeName = valueTypeName
@@ -59,7 +65,7 @@ function TfPropertyTypeError (type, property, label, value, valueTypeName) {
     this.message = 'Unexpected property "' + property + '"'
   }
 
-  Error.captureStackTrace(this, TfTypeError)
+  captureStackTrace(this, TfTypeError)
   this.__label = label
   this.__property = property
   this.__type = type
@@ -90,7 +96,7 @@ function tfSubError (e, property, label) {
     )
   }
 
-  Error.captureStackTrace(e)
+  captureStackTrace(e)
   return e
 }