Allow SVG images to be drawn into canvas without tainting.

https://bugs.webkit.org/show_bug.cgi?id=119492

Reviewed by Darin Adler.

Source/WebCore:

* html/HTMLAnchorElement.cpp:
(WebCore::HTMLAnchorElement::parseAttribute): Call shouldProhibitLinks.
(WebCore::shouldProhibitLinks): Added.
* html/HTMLAnchorElement.h:
* html/HTMLImageElement.cpp:
(WebCore::HTMLImageElement::parseAttribute): Call shouldProhibitLinks.
* rendering/svg/RenderSVGRoot.cpp:
(WebCore::RenderSVGRoot::isEmbeddedThroughSVGImage): Use isInSVGImage.
* svg/SVGAElement.cpp:
(WebCore::SVGAElement::svgAttributeChanged): Call shouldProhibitLinks.
* svg/graphics/SVGImage.cpp:
(WebCore::SVGImage::hasSingleSecurityOrigin): Added.
(WebCore::isInSVGImage): Added.
* svg/graphics/SVGImage.h:

Change-Id: I294821dff7299e3c6a3e1df8f8ff3d855dc16dbd
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153876 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>