Web Inspector: add character data to the DOM section of native memory view

Web Inspector: add character data to the DOM section of native memory view
https://bugs.webkit.org/show_bug.cgi?id=89968

Reviewed by Vsevolod Vlasov.

Count strings referenced from CharacterData node and its descendants
as part of the DOM tree structures in the native memory view.

* dom/CharacterData.cpp:
(WebCore::CharacterData::reportMemoryUsage):
(WebCore):
* dom/CharacterData.h:
(CharacterData):
* dom/MemoryInstrumentation.h:
(MemoryInstrumentation):
(WebCore::MemoryObjectInfo::reportString):
(MemoryObjectInfo):
* inspector/InspectorMemoryAgent.cpp:
(WebCore):
(WebCore::domTreeInfo):
(WebCore::jsExternalResourcesInfo):
(WebCore::InspectorMemoryAgent::getProcessMemoryDistribution):
* inspector/front-end/NativeMemorySnapshotView.js:
(WebInspector.MemoryBlockViewProperties._initialize):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121530 268f45cc-cd09-0410-ab3c-d52691b4dbfc