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This lays the groundwork for doing transform and clip tree construction in one
place. It also cleans up the part of the interface which is exposed in the Blink
API, and separates range records from the tree itself.

BUG=470248

Review URL: https://codereview.chromium.org/1296963002

git-svn-id: svn://svn.chromium.org/blink/trunk@200764 bbb929c8-8fbe-4397-9dbb-9b2b20218538