[] (0) Explicitly allow <canvas> support to be disabled.

Fixing http://www.w3.org/Bugs/Public/show_bug.cgi?id=7662

git-svn-id: http://svn.whatwg.org/webapps@4031 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

  are the element's <a href=#fallback-content>fallback content</a>.</p>

  <p>In interactive visual media, if <a href=#concept-n-script title=concept-n-script>scripting is enabled</a> for the
  <code><a href=#the-canvas-element>canvas</a></code> element, the <code><a href=#the-canvas-element>canvas</a></code> element
  <code><a href=#the-canvas-element>canvas</a></code> element, and if support for <code><a href=#the-canvas-element>canvas</a></code>
  elements has been enabled, the <code><a href=#the-canvas-element>canvas</a></code> element
  <a href=#represents>represents</a> <a href=#embedded-content>embedded content</a> consisting of
  a dynamically created image.</p>

  <a href=#fallback-content>fallback content</a> instead.</p>

  <p>In non-visual media, and in visual media if <a href=#concept-n-noscript title=concept-n-noscript>scripting is disabled</a> for the
  <code><a href=#the-canvas-element>canvas</a></code> element, the <code><a href=#the-canvas-element>canvas</a></code> element
  <code><a href=#the-canvas-element>canvas</a></code> element or if support for <code><a href=#the-canvas-element>canvas</a></code>
  elements has been disabled, the <code><a href=#the-canvas-element>canvas</a></code> element
  <a href=#represents>represents</a> its <a href=#fallback-content>fallback content</a>
  instead.</p>

source

  <p>In interactive visual media, if <span
  title="concept-n-script">scripting is enabled</span> for the
  <code>canvas</code> element, the <code>canvas</code> element
  <code>canvas</code> element, and if support for <code>canvas</code>
  elements has been enabled, the <code>canvas</code> element
  <span>represents</span> <span>embedded content</span> consisting of
  a dynamically created image.</p>


  <p>In non-visual media, and in visual media if <span
  title="concept-n-noscript">scripting is disabled</span> for the
  <code>canvas</code> element, the <code>canvas</code> element
  <code>canvas</code> element or if support for <code>canvas</code>
  elements has been disabled, the <code>canvas</code> element
  <span>represents</span> its <span>fallback content</span>
  instead.</p>