Move StyleSheet to the oilpan heap using transition types.

This makes StyleSheets RefCountedGarbageCollected. Next step is
removing RefPtrs and raw pointers and dealing with finalization
order issues.

R=erik.corry@gmail.com, haraken@chromium.org, wibling@chromium.org
BUG=

Review URL: https://codereview.chromium.org/187313005

git-svn-id: svn://svn.chromium.org/blink/trunk@168583 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Implement recursive viewport for the Heap Summary view

BUG=255363

Review URL: https://codereview.chromium.org/187823003

git-svn-id: svn://svn.chromium.org/blink/trunk@168584 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Convert some Shape code to use references

This change makes shapes implementation inline with webkit's.
Also using references is lot safe for caller method and
also removes extra null checks.

Insprired by https://bugs.webkit.org/show_bug.cgi?id=124876

Review URL: https://codereview.chromium.org/178473024

git-svn-id: svn://svn.chromium.org/blink/trunk@168585 bbb929c8-8fbe-4397-9dbb-9b2b20218538