Add toImplSequence()

third_party/WebKit/Source/bindings/core/v8/V8Binding.h

Index: third_party/WebKit/Source/bindings/core/v8/V8Binding.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
index 3d5ea9e20f91f19ec507c2cf2548f142e2cfce26..cde8cb190c646b03dbca071c81ca8bdd4043e600 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
+++ b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
@@ -728,6 +728,61 @@ VectorType toImplArguments(const v8::FunctionCallbackInfo<v8::Value>& info, int
     return result;
 }
 
+// Gets an iterator from an Object.
+v8::MaybeLocal<v8::Object> getIterator(v8::Local<v8::Object>, v8::Isolate*, ExceptionState&);

[haraken, 2016/09/08 09:32:08]

I don't have any strong opinion but might prefer returning
v8::Local<v8::Object>. i.e., return an empty handle when the iterator is not
available.

[bashi, 2016/09/09 00:54:22]

I think using MaybeLocal has two advantages:
1. Caller must check empty handles
2.
  - !MaybeLocal.ToLocal() -> We are sure that there is an exception.
  - Local.IsEmpty() -> No information.

MaybeLocal is useful in some cases. We shouldn't avoid using it too much.

+
+// Converts a V8 value to an array (an IDL sequence) as per the WebIDL
+// specification: http://heycam.github.io/webidl/#es-sequence
+template <typename VectorType>
+VectorType toImplSequence(v8::Local<v8::Value> value, v8::Isolate* isolate, ExceptionState& exceptionState)

[Yuki, 2016/09/08 08:32:21]

Could you make v8::Isolate* the first argument?

[bashi, 2016/09/09 00:54:23]

Done. Having said that it's inconsistent with other array or sequence conversion
functions like toImplArray(). I'm not sure putting isolate first makes sense at
this point. (I don't want to change other signatures in this CL)

+{
+    typedef typename VectorType::ValueType ValueType;

[Yuki, 2016/09/08 08:32:21]

I guess
    using VectorType::ValueType;
does the trick.

[bashi, 2016/09/09 00:54:22]

Done.

+
+    if (!value->IsObject() || value->IsRegExp()) {
+        exceptionState.throwTypeError("The provided value cannot be converted to a sequence.");
+        return VectorType();
+    }
+
+    v8::Local<v8::Object> iterator;
+    if (!getIterator(value.As<v8::Object>(), isolate, exceptionState).ToLocal(&iterator))
+        return VectorType();
+
+    v8::Local<v8::String> nextKey = v8String(isolate, "next");
+    v8::Local<v8::String> valueKey = v8String(isolate, "value");
+    v8::Local<v8::String> doneKey = v8String(isolate, "done");
+    v8::Local<v8::Context> context = isolate->GetCurrentContext();
+    VectorType result;
+    while (true) {
+        v8::Local<v8::Value> next;
+        if (!iterator->Get(context, nextKey).ToLocal(&next))
+            return VectorType();
+        if (!next->IsObject() || !next.As<v8::Object>()->IsCallable()) {
+            exceptionState.throwTypeError("The next property should be callable.");

[Yuki, 2016/09/08 08:32:21]

I think
  "Iterator.next should be callable."
is easier to understand, like below.

[bashi, 2016/09/09 00:54:23]

Done.

+            return VectorType();
+        }
+        v8::Local<v8::Value> nextResult;
+        if (!next.As<v8::Object>()->CallAsFunction(context, iterator, 0, nullptr).ToLocal(&nextResult))
+            return VectorType();

[haraken, 2016/09/08 09:32:08]

Don't we need to throw an exception?

[bashi, 2016/09/09 00:54:23]

No, as described in another reply.

+        if (!nextResult->IsObject()) {
+            exceptionState.throwTypeError("Iterator.next() does not return an object.");

[Yuki, 2016/09/08 08:32:21]

s/does/did/

[bashi, 2016/09/09 00:54:23]

Done.

+            return VectorType();
+        }
+        v8::Local<v8::Object> resultObject = nextResult.As<v8::Object>();
+        v8::Local<v8::Value> element;
+        v8::Local<v8::Value> done;
+        if (!resultObject->Get(context, valueKey).ToLocal(&element)
+            || !resultObject->Get(context, doneKey).ToLocal(&done))
+            return VectorType();

[haraken, 2016/09/08 09:32:08]

Ditto.

+        v8::Local<v8::Boolean> doneBoolean;
+        if (!done->ToBoolean(context).ToLocal(&doneBoolean))
+            return VectorType();

[haraken, 2016/09/08 09:32:08]

Ditto.

+        result.uncheckedAppend(NativeValueTraits<ValueType>::nativeValue(isolate, element, exceptionState));
+        if (doneBoolean->Value())
+            break;
+    }
+    return result;
+}
+
 // Validates that the passed object is a sequence type per WebIDL spec
 // http://www.w3.org/TR/2012/CR-WebIDL-20120419/#es-sequence
 inline bool toV8Sequence(v8::Local<v8::Value> value, uint32_t& length, v8::Isolate* isolate, ExceptionState& exceptionState)