Parse new circle shape syntax

Implement parsing of the new circle shape syntax. The implementation of
the old syntax has been move aside as deprecated, and will be removed
once the new syntax is stable.

Updated existing parsing tests to cover this.

Patch by Bem Jones-Bey.

BUG=322165

Review URL: https://codereview.chromium.org/98723006

git-svn-id: svn://svn.chromium.org/blink/trunk@164131 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rename LinkImport::m_loader LinkImport::m_child

This follows the typename change.

BUG=none
TEST=none
R=tkent,dglazkov,dominicc

Review URL: https://codereview.chromium.org/111953009

git-svn-id: svn://svn.chromium.org/blink/trunk@164132 bbb929c8-8fbe-4397-9dbb-9b2b20218538