Implement canHaveWhitespaceChildren on RenderSVG{Root,ModelObject}

Implement canHaveWhitespaceChildren on RenderSVG{Root,ModelObject}

Make said method return false to signal that we don't care about
whitespace-only Nodes in these contexts.
This avoids creating large number of text RenderObjects
(RenderSVGInlineTexts) and also avoids hitting the linear search
at the bottom of Text::textRendererIsNeeded.

R=pdr,schenney,fmalita
BUG=339470, 337607
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166238

[f(malita), 2014-01-31 15:45:22]

lgtm

[fs, 2014-01-31 17:14:12]

The CQ bit was checked by fs@opera.com

[commit-bot: I haz the power, 2014-01-31 17:14:37]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/fs@opera.com/136963005/1

[commit-bot: I haz the power, 2014-01-31 19:51:28]

Change committed as 166238

[commit-bot: I haz the power, 2014-01-31 19:51:32]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 19:51:34]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 19:51:35]

CQ bit was unchecked on CL. Ignoring.