Implement ImageData constructors.

Source/core/html/ImageData.idl

Index: Source/core/html/ImageData.idl
diff --git a/Source/core/html/ImageData.idl b/Source/core/html/ImageData.idl
index 06847999097b6b94586674ca8ec7d7459cefe45b..881b1551eceb98668426ef434af86c8598903751 100644
--- a/Source/core/html/ImageData.idl
+++ b/Source/core/html/ImageData.idl
@@ -27,7 +27,9 @@
  */
 
 [
+    CustomConstructor,

[Inactive, 2014/03/19 18:59:48]

Even if the constructor is custom, you're expected to provide the prototype of
the constructor (e.g. CustomConstructor(float x, float y)). The bindings
generator relies on that to compute the correct value for
window.ImageData.length property.

Also, are you sure we need to have custom code if we put the constructor in this
specific order in the IDL?
[
    Constructor(Uint8ClampedArray data, unsigned long sw, optional unsigned long
sh),
    Constructor(unsigned long sw, unsigned long sh),
]

iirc, if we put the most specific arg type first, our bindings generator does
the right thing(tm). I may be wrong but it is worth trying I think.

[sof, 2014/03/19 19:20:34]

On 2014/03/19 18:59:48, Chris Dumez wrote:
...
That's not the reason behind the custom constructor, but the provision of "data"
on the wrapper to optimize its access. 

(Yes, what you suggest gives a reasonable overloading -- see patchset #1.)

[sof, 2014/03/19 22:19:16]

Added along with a test for expected constructor "length".

     Custom=Wrap,
+    RaisesException=Constructor,
 ] interface ImageData {
     readonly attribute long width;
     readonly attribute long height;