resolve <defs>

[leungwensen]

complex SVG icons using <defs> (for reusing paths, enable gradients, etc.) can not be rendered properly if simply replace <svg> into <symbol>. <defs> should be placed just under root level.

[leungwensen]

conclusion:

• removing style="display:none;" in <svg> tag can solve this for webkit-based browsers;
• extracting gradients should fix this problem for IE and Firefox.

[Tklaversma]

Besides that fact that you have a bug when not using <defs>, it is also not compliant to the SVG 1.1 spec, which states the use of <defs>.

Also see #14.