[Webkit-unassigned] [Bug 22390] New: Abstract away JSC:: usage in WebCore/xml

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=22390

           Summary: Abstract away JSC:: usage in WebCore/xml
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: darin at chromium.org


Abstract away JSC:: usage in WebCore/xml

There is just a small bit of XMLHttpRequest code that uses JSC::Value*
directly.  It uses it to provide a fast responseText getter to JS.

This is a proposal to define a ScriptString class that acts like a holder for a
JSC::UString.  XMLHttpRequest::m_responseText is modified to be a ScriptString
instead of a JSC::UString.  ScriptString can be implicitly converted to UString
for convenience.

Along the way, I found that there is no UString specific jsStringOrNull, which
means that the optimization of storing responseText as a UString was basically
being defeated due to an implicit conversion to String.  It turns out that
providing a jsStringOrNull that takes a UString causes 'ambiguous implicit
conversion' errors elsewhere (see JSElement.cpp), but using ScriptString works
fine, so I have done that to help performance of accessing responseText.

If this proposal looks good, then I'll do a follow-up patch that applies
ScriptString elsewhere.  For now, I am just focused on the WebCore/xml
directory.


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