Remove profile and baseProfile getters from HeapSnapshotView

They used profile uid to introduce unnecessary indirection between view and profile. We can store reference to the profile object directly.

BUG=None
R=alph@chromium.org

Review URL: https://codereview.chromium.org/146963005

git-svn-id: svn://svn.chromium.org/blink/trunk@165853 bbb929c8-8fbe-4397-9dbb-9b2b20218538