Web Inspector: provide basic information about DOM character data size

Web Inspector: provide basic information about DOM character data size
https://bugs.webkit.org/show_bug.cgi?id=76059

Memory agent allows to estimate size of DOM character data and size of WebCore
strings held by JavaScript objects.

Reviewed by Pavel Feldman.

* bindings/js/ScriptProfiler.h:
(WebCore::ScriptProfiler::visitExternalJSStrings):
* bindings/v8/ScriptProfiler.cpp:
(WebCore::ScriptProfiler::visitExternalJSStrings):
* bindings/v8/ScriptProfiler.h:
* bindings/v8/V8Binding.cpp:
(WebCore::WebCoreStringResource::visitStrings):
(WebCore::V8BindingPerIsolateData::visitJSExternalStrings):
* bindings/v8/V8Binding.h:
* inspector/DOMWrapperVisitor.h:
* inspector/Inspector.json:
* inspector/InspectorMemoryAgent.cpp:
(WebCore::CharacterDataStatistics::DOMTreeStatistics::DOMTreeStatistics):
(WebCore::CharacterDataStatistics::DOMTreeStatistics::collectNodeStatistics):
(WebCore::CharacterDataStatistics::CounterVisitor::CounterVisitor):
(WebCore::CharacterDataStatistics::CounterVisitor::domGroups):
(WebCore::CharacterDataStatistics::CounterVisitor::strings):
(WebCore::CharacterDataStatistics::CounterVisitor::visitNode):
(WebCore::CharacterDataStatistics::CounterVisitor::visitJSExternalString):
(WebCore::InspectorMemoryAgent::getDOMNodeCount):
* inspector/InspectorMemoryAgent.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105157 268f45cc-cd09-0410-ab3c-d52691b4dbfc