https://bugs.webkit.org/show_bug.cgi?id=19121
Serializer doesn't handling inconsistent prefixes properly
https://bugs.webkit.org/show_bug.cgi?id=117764
Attribute namespaces are serialized as if they were element ones
https://bugs.webkit.org/show_bug.cgi?id=22958

Reviewed by Ryosuke Niwa.

Source/WebCore:

Add code to make sure unique prefixes and namespace declarations are generated.
Unique prefix generation happens when:
- the same prefix is used to map to different namespaces or
- no prefix is given but the attribute is in a namespace.

This is done in order to not violate constraints listed in http://www.w3.org/TR/xml-names11/. In general
the pseudo code listed in http://www.w3.org/TR/DOM-Level-3-Core/namespaces-algorithms.html#normalizeDocumentAlgo
is used, doing the following for attributes:
if the attribute has a namespace then
  if the attribute has no prefix OR prefix is not declared OR conflicts with existing prefix mapping to different NS then
    try to find the matching in-scope declaration by looking up the prefix in the namespace -> prefix mapping, if found use that prefix
    else if the attribute prefix is not null AND not mapped in-scope, declare the prefix
    else generate a unique prefix for the namespace

To keep track of in-scope namespaces a prefix to namespace mapping is used.

Tests: fast/dom/XMLSerializer-attribute-namespace-prefix-conflicts.html
       fast/dom/XMLSerializer-same-prefix-different-namespaces-conflict.html
       fast/dom/XMLSerializer-setAttributeNS-namespace-no-prefix.html
       svg/custom/xlink-prefix-generation-in-attributes.html

* editing/MarkupAccumulator.cpp:
(WebCore::MarkupAccumulator::MarkupAccumulator):
(WebCore::MarkupAccumulator::shouldAddNamespaceAttribute):
(WebCore::MarkupAccumulator::appendNamespace):
(WebCore::MarkupAccumulator::generateUniquePrefix):
(WebCore::MarkupAccumulator::appendAttribute):
* editing/MarkupAccumulator.h:

LayoutTests:

Add tests to make sure unique prefixes and namespace declarations are generated for the
case when the same prefix is used to map to different namespaces. All testcases are based
on the testcases attached to the bugs.

* fast/dom/XMLSerializer-attribute-namespace-prefix-conflicts-expected.txt: Added.
* fast/dom/XMLSerializer-attribute-namespace-prefix-conflicts.html: Added.
* fast/dom/XMLSerializer-same-prefix-different-namespaces-conflict-expected.txt: Added.
* fast/dom/XMLSerializer-same-prefix-different-namespaces-conflict.html: Added.
* fast/dom/XMLSerializer-setAttributeNS-namespace-no-prefix-expected.txt: Added.
* fast/dom/XMLSerializer-setAttributeNS-namespace-no-prefix.html: Added.
* svg/custom/xlink-prefix-generation-in-attributes-expected.txt: Added.
* svg/custom/xlink-prefix-generation-in-attributes.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154779 268f45cc-cd09-0410-ab3c-d52691b4dbfc