[flot] returned canvas reuse
[flot] returned canvas reuse

This gives us _massive_ improvement in memory use. Before that Chrome
could easily grab as much as 400M for heap, with this patch it seems
to stay way below 100M.

This basically reverts 6fe0258642cf1c465be3a9b5bee1005cd46a2d59 back.
Which applied flot patch from here:
http://code.google.com/p/flot/issues/detail?id=269

Change-Id: Icf9bd8d828c1c36e4fdd0886bca44407148ef2b7
Reviewed-on: http://review.membase.org/3319
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

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