[Content Extensions] Use less memory for CombinedURLFilters.

[Content Extensions] Use less memory for CombinedURLFilters.
https://bugs.webkit.org/show_bug.cgi?id=144290

Patch by Alex Christensen <achristensen@webkit.org> on 2015-04-28
Reviewed by Andreas Kling.

Source/WebCore:

* contentextensions/CombinedURLFilters.cpp:
(WebCore::ContentExtensions::recursiveMemoryUsed):
(WebCore::ContentExtensions::CombinedURLFilters::addPattern):
(WebCore::ContentExtensions::generateNFAForSubtree):
(WebCore::ContentExtensions::CombinedURLFilters::createNFAs):
* contentextensions/NFA.cpp:
(WebCore::ContentExtensions::NFA::memoryUsed):
(WebCore::ContentExtensions::NFA::setActions):
* contentextensions/NFA.h:
* contentextensions/NFANode.h:
* contentextensions/Term.h:
(WebCore::ContentExtensions::Term::Term::generateGraph):
(WebCore::ContentExtensions::Term::generateSubgraphForAtom):
Use Vectors instead of HashTables in PrefixTreeVertex because the sets stay small and need to be more memory efficient.

Source/WTF:

* wtf/Forward.h:
* wtf/Vector.h:
Added a minCapacity template parameter to allow changing the minimum size of an
allocated buffer. The default minCapacity is kept at 16 unless otherwise specified
to have no change on existing code, but this could be changed later. A smaller
default minCapacity would use less memory with small Vectors but spend more time
copying when expanding to large Vectors.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@183499 268f45cc-cd09-0410-ab3c-d52691b4dbfc