Add an example of embedding a Skia Perf graph to the site docs.

This specific page:

  https://skia.org/dev/testing/skiaperf?cl=1462583002

BUG=skia:
NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=1462583002

Review URL: https://codereview.chromium.org/1462583002
1 file changed