Add ByteString support to IDL bindings

Source/bindings/v8/V8Binding.cpp

Index: Source/bindings/v8/V8Binding.cpp
diff --git a/Source/bindings/v8/V8Binding.cpp b/Source/bindings/v8/V8Binding.cpp
index b928d011e2ce29dc0817582dc9b977fbe3fcd7a2..bef984e7af5aff1ac0aafda305d59436dbe6173d 100644
--- a/Source/bindings/v8/V8Binding.cpp
+++ b/Source/bindings/v8/V8Binding.cpp
@@ -492,6 +492,31 @@ float toFloat(v8::Handle<v8::Value> value, ExceptionState& exceptionState)
     return numberObject->NumberValue();
 }
 
+String toByteString(v8::Handle<v8::Value> value, ExceptionState& exceptionState)
+{
+    // Handle [Default=NullString]
+    if (value.IsEmpty())
+        return String();
+
+    // From the Web IDL spec: http://heycam.github.io/webidl/#es-ByteString
+
+    // 1. Let x be ToString(v)
+    TONATIVE_DEFAULT_EXCEPTIONSTATE(v8::Local<v8::String>, stringObject, value->ToString(), exceptionState, String());
+    String x = toCoreString(stringObject);

[haraken, 2014/06/11 03:54:52]

I'm not quite sure, but probably this should be:

TOSTRING_DEFAULT(V8StringResource<>, string, value, String());

?

[Nils Barth (inactive), 2014/06/11 03:59:47]

Oh, that's a good point, I think.
We're only throwing the exception here, not in the string conversion, so we
don't need to pass exceptionState to the macro, right?

(OTOH, in the *generated bindings* we do need to use the ES macro b/c this code
can throw an exception.)

[jsbell, 2014/06/11 16:55:06]

Just to make sure I'm understanding things - TOSTRING_DEFAULT uses
V8StringResource and calls prepare(). If the ES 'ToString()' conversion itself
throws, the prepare() catches and rethrows it. But the C++ code should just
blithely carry on? Does that work properly in a context such as this where
exceptionState is passed in?

[jsbell, 2014/06/11 16:57:43]

And to be clear, the TONATIVE_DEFAULT_EXCEPTIONSTATE is handling the ToString()
throwing (which sets an exception via exceptionState, then returns early).

I believe I can switch to TOSTRING_DEFAULT() but that seems... weird. I don't
see it being used in conjunction with an exceptionState anywhere.

[haraken, 2014/06/11 23:55:16]

You're right. Your programming pattern matches what toInt32() does. So LGTM.

Sorry about the noise!

+
+    // 2. If the value of any element of x is greater than 255, then throw a TypeError.
+    if (!x.containsOnlyLatin1()) {
+        exceptionState.throwTypeError("Value is not a valid ByteString.");
+        return String();
+    }
+
+    // 3. Return an IDL ByteString value whose length is the length of x, and where the
+    // value of each element is the value of the corresponding element of x.
+    // Blink: A ByteString is simply a String with a range constrained per the above, so
+    // this is the identity operation.
+    return x;
+}
+
 PassRefPtrWillBeRawPtr<XPathNSResolver> toXPathNSResolver(v8::Handle<v8::Value> value, v8::Isolate* isolate)
 {
     RefPtrWillBeRawPtr<XPathNSResolver> resolver = nullptr;