Prevent reading stale/invalid data when applying a <pattern>

Prevent reading stale/invalid data when applying a <pattern>

RenderSVGResourcePattern::applyResource was checking the value of
PatternAttributes::patternUnits() before it had been set from the element,
meaning it could have been stale after having been updated, or plain wrong
since the default value is oBB.
Hoist the PatternAttribute setup out of buildPattern() to make sure
|m_attributes| is valid when read.
The |resourceMode| attribute passed to buildPattern() is removed because
it is unused.

BUG=415619
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=182268

[fs, 2014-09-18 16:08:07]

fs@opera.com changed reviewers:
+ fmalita@chromium.org, pdr@chromium.org, schenney@chromium.org

[f(malita), 2014-09-18 20:45:33]

The CQ bit was checked by fmalita@chromium.org

[f(malita), 2014-09-18 20:45:33]

lgtm

[commit-bot: I haz the power, 2014-09-18 20:46:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/579243004/1

[commit-bot: I haz the power, 2014-09-18 20:52:34]

Committed patchset #1 (id:1) as 182268