When converting a non-finite float, throw the TypeError from the FromJSValConvertible implementation.

This removes some unnecessary custom code in the codegen and makes this
implementation follow the convention of having thrown an exception when
returning Err() from FromJSValConvertible.

components/script/dom/bindings/codegen/CodegenRust.py

@@ -887,17 +887,6 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
     if type.nullable():
         declType = CGWrapper(declType, pre="Option<", post=">")
 
-    template = ""
-    if type.isFloat() and not type.isUnrestricted():
-        template = (
-            "match FromJSValConvertible::from_jsval(cx, ${val}, ()) {\n"
-            "    Ok(v) => v,\n"
-            "    Err(_) => {\n"
-            "       throw_type_error(cx, \"this argument is not a finite floating-point value\");\n"
-            "       %s\n"
-            "    }\n"
-            "}" % exceptionCode)
-    else:
     #XXXjdm support conversionBehavior here
     template = (
         "match FromJSValConvertible::from_jsval(cx, ${val}, ()) {\n"

components/script/dom/bindings/conversions.rs

@@ -33,6 +33,7 @@
 //! | union types             | `T`                              |
 
 use dom::bindings::codegen::PrototypeList;
+use dom::bindings::error::throw_type_error;
 use dom::bindings::js::{JSRef, Root, Unrooted};
 use dom::bindings::num::Finite;
 use dom::bindings::str::{ByteString, USVString};
@@ -288,7 +289,10 @@ impl<T: Float + FromJSValConvertible<Config=()>> FromJSValConvertible for Finite
         let result = try!(FromJSValConvertible::from_jsval(cx, value, option));
         match Finite::new(result) {
             Some(v) => Ok(v),
-            None => Err(()),
+            None => {
+                throw_type_error(cx, "this argument is not a finite floating-point value");
+                Err(())
+            },
         }
     }
 }