Implement a part of ProcessingInstruction by using PrivateScript

Source/core/dom/Document.idl

Index: Source/core/dom/Document.idl
diff --git a/Source/core/dom/Document.idl b/Source/core/dom/Document.idl
index 4a640c8fd6a07e09639c7a449d83b7bead584d22..f0c63273d2f6589d5806bd690895ab5b6d0e4d71 100644
--- a/Source/core/dom/Document.idl
+++ b/Source/core/dom/Document.idl
@@ -215,6 +215,10 @@ typedef (CanvasRenderingContext2D or WebGLRenderingContext) RenderingContext;
     [MeasureAs=PrefixedPageVisibility, ImplementedAs=hidden] readonly attribute boolean webkitHidden;
 
     readonly attribute HTMLScriptElement currentScript;
+
+    // Internal API for XSLT
+    [OnlyExposedToPrivateScript] void applyXSLTransform(ProcessingInstruction styleSheet);
+    [OnlyExposedToPrivateScript] readonly attribute Document transformSourceDocument;

[abarth-chromium, 2014/08/05 18:51:41]

I'm concerned about adding a bunch of private APIs to support XSLT-in-JS.  Do
you have a design doc that explains what private APIs we'll need?

It seems like applyXSLTransform and transformSourceDocument could be implemented
in JavaScript.  Is that the eventual plan?  For example, you could imagine
implementing XSLT processing directives entirely in JavaScript based on
window.XSLTProcessor...  In that approach, you wouldn't need these private APIs.

[tasak, 2014/08/06 02:52:03]

Yeah, I would like to remove applyXSLTransform and transformDocument from
Document.{h,cpp}.

However, I think, probably we need C++ special method for PrivateScript, i.e.
- setXSLStyleSheet, and
- createDocumentFromSource

setXSLStyleSheet is a special method to specify XSLStyleSheet, but
XSLTProcessor.idl provides importStyleSheet.

createDocumentFromSource replaces a current frame's document, e.g. XMLDocument
(before applying XSLStyleSheet) => HTMLDocument (after applying XSLStyleSheet).

The above methods are used in Document::applyXSLTransform but not public in web.

My plan is:
- some part of C++ applyXSLTransform will be re-implemented by using 
Javascript,
- the left C++ applyXSLTransform is moved into XSLTProcessor (private method for
PrivateScript).
- transformSourceDocument will be re-implemented by using Javascript

 };
 
 Document implements GlobalEventHandlers;