Implement ImageData constructors.

Source/bindings/tests/idls/TestInterfacePython2.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 // This is for interface extended attributes that interact with another extended
 // attribute, and thus both cannot be tested at once.
 // The more *minor* extended attribute should be put in this file.
 
 [
+    Constructor(int width),
     Custom=Wrap,  // Conflicts with and [Custom=ToV8], respectively
     DependentLifetime,  // Covered by [ActiveDOMObject]
     SetWrapperReferenceFrom=ownerNode,  // Conflicts with [SetWrapperReferenceTo]
     SpecialWrapFor=Interface1|Interface2,  // Conflicts with [Custom=ToV8]
 ] interface TestInterfacePython2 {
 };