https://bugs.webkit.org/show_bug.cgi?id=72198
This patch ensures that:
- Dense arrays are serialized densly, and not as name-value pairs
- Sparse arrays are allocated as sparse on deserialization.
The criteria to choose whether to serialize densly or sparsely is the size
of a resulting serialized stream.

Reviewed by David Levin.

Test: fast/dom/Window/window-postmessage-arrays.html

* bindings/v8/SerializedScriptValue.cpp:
(WebCore::V8ObjectMap::Writer::writeDenseArray):
(WebCore::V8ObjectMap::Writer::writeGenerateFreshSparseArray):
(WebCore::V8ObjectMap::Writer::writeGenerateFreshDenseArray):
(WebCore::V8ObjectMap::Serializer::writeDenseArray):
(WebCore::V8ObjectMap::Serializer::AbstractObjectState::execDepth):
(WebCore::V8ObjectMap::Serializer::AbstractObjectState::serializeProperties):
(WebCore::V8ObjectMap::Serializer::ObjectState::advance):
(WebCore::V8ObjectMap::Serializer::DenseArrayState::DenseArrayState):
(WebCore::V8ObjectMap::Serializer::DenseArrayState::advance):
(WebCore::V8ObjectMap::Serializer::DenseArrayState::objectDone):
(WebCore::V8ObjectMap::Serializer::SparseArrayState::SparseArrayState):
(WebCore::V8ObjectMap::Serializer::SparseArrayState::advance):
(WebCore::V8ObjectMap::Serializer::serializeDensely):
(WebCore::V8ObjectMap::Serializer::startArrayState):
(WebCore::V8ObjectMap::Serializer::startObjectState):
(WebCore::V8ObjectMap::Serializer::doSerialize):
(WebCore::V8ObjectMap::Reader::read):
(WebCore::V8ObjectMap::Deserializer::newSparseArray):
(WebCore::V8ObjectMap::Deserializer::completeSparseArray):
(WebCore::V8ObjectMap::Deserializer::completeDenseArray):

LayoutTests: [V8][Chromium]Serialize dense arrays densly.
https://bugs.webkit.org/show_bug.cgi?id=72198

Reviewed by David Levin.

* fast/dom/Window/script-tests/postmessage-clone.js:
* fast/dom/Window/window-postmessage-arrays-expected.txt: Added.
* fast/dom/Window/window-postmessage-arrays.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@100239 268f45cc-cd09-0410-ab3c-d52691b4dbfc