[giow] (2) Revamp the way that type='' on <link> is defined to actual…

…ly be accurate. Allow sniffing when the expected type is an image.

git-svn-id: http://svn.whatwg.org/webapps@1784 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

@@ -7666,7 +7666,8 @@ background: transparent">blue&lt;/span>.&lt;/p></pre>
    then the <code title=attr-link-media><a href="#media0">media</a></code>
    attribute is prescriptive. The user agent must apply the external resource
    to <span>views</span><!-- XXX xref --> while their state match the listed
-   media, and must not apply them otherwise.
+   media and the other relevant conditions apply, and must not apply them
+   otherwise.
 
   <p id=default-media>The default, if the <code title=attr-link-media><a
    href="#media0">media</a></code> attribute is omitted, is <code>all</code>,
@@ -7685,26 +7686,48 @@ background: transparent">blue&lt;/span>.&lt;/p></pre>
    href="#refsRFC2046">[RFC2046]</a>
 
   <p>For <a href="#links1" title="external resource link">external resource
-   links</a>, user agents may use the type given in this attribute to decide
-   whether or not to consider using the resource at all. If the UA does not
-   support the given MIME type for the given link relationship, then the UA
-   may opt not to download and apply the resource.
+   links</a>, the <code title=attr-link-type><a href="#type">type</a></code>
+   attribute is used as a hint to user agents so that they can avoid
+   downloading resources they do not support. If the attribute is present,
+   then the user agent must assume that the resource is of the given type. If
+   the attribute is omitted, but the external resource link type has a
+   default type defined, then the user agent must assume that the resource is
+   of that type. If the UA does not support the given MIME type for the given
+   link relationship, then the UA should not download the resource; if the UA
+   does support the given MIME type for the given link relationship, then the
+   UA should download the resource. If the attribute is omitted, and the
+   external resource link type does not have a default type defined, but the
+   user agent would fetch the resource if the type was known and supported,
+   then the user agent should fetch the resource under the assumption that it
+   will be supported.
 
   <p>User agents must not consider the <code title=attr-link-type><a
    href="#type">type</a></code> attribute authoritative &mdash; upon fetching
-   the resource, user agents must not use metadata included in the link to
-   the resource to determine its type.
-
-  <p>If the attribute is omitted, but the user agent would fetch the resource
-   if the type was known and supported, then the user agent must fetch the
-   resource and determine its type <a href="#content-type8"
-   title=Content-Type>from its Content-Type metadata</a> to determine if it
-   supports (and can apply) that external resource. If no type metadata is
-   specified, but the external resource link type has a default type defined,
-   then the user agent must assume that the resource is of that type.
+   the resource, user agents must not use the <code title=attr-link-type><a
+   href="#type">type</a></code> attribute to determine its actual type. Only
+   the actual type (as defined in the next paragraph) is used to determine
+   whether to <em>apply</em> the resource, not the aforementioned assumed
+   type.
+
+  <p>If the resource is expected to be an image, user agents may apply the <a
+   href="#content-type6" title="Content-Type sniffing: image">image sniffing
+   rules</a>, with the <var title="">official type</var> being the type
+   determined from the resource's <a href="#content-type8"
+   title=Content-Type>Content-Type metadata</a>, and use the resulting
+   sniffed type of the resource as if it was the actual type. Otherwise, if
+   the resource is not expected to be an image, or if the user agent opts not
+   to apply those rules, then the user agent must use the resource's <a
+   href="#content-type8" title=Content-Type>Content-Type metadata</a> to
+   determine the type of the resource. If there is no type metadata, but the
+   external resource link type has a default type defined, then the user
+   agent must assume that the resource is of that type.
+
+  <p>Once the user agent has established the type of the resource, the user
+   agent must apply the resource if it is of a supported type and the other
+   relevant conditions apply, and must ignore the resource otherwise.
 
   <div class=example>
-   <p>If a document contains four style sheet links labeled as follows:</p>
+   <p>If a document contains style sheet links labeled as follows:</p>
 
    <pre>&lt;link rel="stylesheet" href="A" type="text/plain"&gt;
 &lt;link rel="stylesheet" href="B" type="text/css"&gt;
@@ -34085,8 +34108,8 @@ user reload must be equivalent to .reload()
   <p>User agents must ignore any rows for image types that they do not
    support.
 
-  <p>Otherwise, the <i>sniffed type</i> of the resource is the same as its
-   <var title="">official type</var>.
+  <p>Otherwise, the sniffed type of the resource is the same as its <var
+   title="">official type</var>.
 
   <h4 id=content-type3><span class=secno>4.10.4 </span><dfn
    id=content-type7>Content-Type sniffing: feed or HTML</dfn></h4>

source

@@ -6041,7 +6041,8 @@ background: transparent">blue&lt;/span>.&lt;/p></pre>
   then the <code title="attr-link-media">media</code> attribute is
   prescriptive. The user agent must apply the external resource to
   <span>views</span><!-- XXX xref --> while their state match the
-  listed media, and must not apply them otherwise.</p>
+  listed media and the other relevant conditions apply, and must not
+  apply them otherwise.</p>
 
   <p id="default-media">The default, if the <code
   title="attr-link-media">media</code> attribute is omitted, is
@@ -6059,30 +6060,52 @@ background: transparent">blue&lt;/span>.&lt;/p></pre>
   href="#refsRFC2046">[RFC2046]</a></p>
 
   <p>For <span title="external resource link">external resource
-  links</span>, user agents may use the type given in this attribute
-  to decide whether or not to consider using the resource at all. If
-  the UA does not support the given MIME type for the given link
-  relationship, then the UA may opt not to download and apply the
-  resource.</p>
+  links</span>, the <code title="attr-link-type">type</code> attribute
+  is used as a hint to user agents so that they can avoid downloading
+  resources they do not support. If the attribute is present, then the
+  user agent must assume that the resource is of the given type. If
+  the attribute is omitted, but the external resource link type has a
+  default type defined, then the user agent must assume that the
+  resource is of that type. If the UA does not support the given MIME
+  type for the given link relationship, then the UA should not
+  download the resource; if the UA does support the given MIME type
+  for the given link relationship, then the UA should download the
+  resource. If the attribute is omitted, and the external resource
+  link type does not have a default type defined, but the user agent
+  would fetch the resource if the type was known and supported, then
+  the user agent should fetch the resource under the assumption that
+  it will be supported.</p>
 
   <p>User agents must not consider the <code
   title="attr-link-type">type</code> attribute authoritative &mdash;
-  upon fetching the resource, user agents must not use metadata
-  included in the link to the resource to determine its type.</p>
-
-  <p>If the attribute is omitted, but the user agent would fetch the
-  resource if the type was known and supported, then the user agent
-  must fetch the resource and determine its type <span
-  title="Content-Type">from its Content-Type metadata</span> to
-  determine if it supports (and can apply) that external resource. If
-  no type metadata is specified, but the external resource link type
-  has a default type defined, then the user agent must assume that the
-  resource is of that type.</p>
+  upon fetching the resource, user agents must not use the <code
+  title="attr-link-type">type</code> attribute to determine its actual
+  type. Only the actual type (as defined in the next paragraph) is
+  used to determine whether to <em>apply</em> the resource, not the
+  aforementioned assumed type.</p>
+
+  <p>If the resource is expected to be an image, user agents may apply
+  the <span title="Content-Type sniffing: image">image sniffing
+  rules</span>, with the <var title="">official type</var> being the
+  type determined from the resource's <span
+  title="Content-Type">Content-Type metadata</span>, and use the
+  resulting sniffed type of the resource as if it was the actual
+  type. Otherwise, if the resource is not expected to be an image, or
+  if the user agent opts not to apply those rules, then the user agent
+  must use the resource's <span title="Content-Type">Content-Type
+  metadata</span> to determine the type of the resource. If there is
+  no type metadata, but the external resource link type has a default
+  type defined, then the user agent must assume that the resource is
+  of that type.</p>
+
+  <p>Once the user agent has established the type of the resource, the
+  user agent must apply the resource if it is of a supported type and
+  the other relevant conditions apply, and must ignore the resource
+  otherwise.</p>
 
   <div class="example">
 
-   <p>If a document contains four style sheet links labeled as
-   follows:</p>
+   <p>If a document contains style sheet links labeled as follows:</p>
 
    <pre>&lt;link rel="stylesheet" href="A" type="text/plain"&gt;
 &lt;link rel="stylesheet" href="B" type="text/css"&gt;
@@ -31802,7 +31825,7 @@ user reload must be equivalent to .reload()
   <p>User agents must ignore any rows for image types that they do not
   support.</p>
 
-  <p>Otherwise, the <i>sniffed type</i> of the resource is the same as
+  <p>Otherwise, the sniffed type of the resource is the same as
   its <var title="">official type</var>.</p>