Add "validate share data" algorithm

index.html

@@ -161,32 +161,18 @@ 
             
             [=Consume user activation=] of |window|.
             
-            If none of |data|'s members {{ShareData/title}},
-            {{ShareData/text}}, or {{ShareData/url}} or {{ShareData/files}} are
-            present, return a promise rejected with a {{TypeError}}.
+            Let |base:URL| be [=this=]'s relevant settings object's
+            [=environment settings object/API base URL=].
             
-            If |data|'s {{ShareData/files}} member is present:
-              
-                If |data|'s {{ShareData/files}} member is empty, or if the
-                implementation does not support file sharing, return a
-                promise rejected with a {{TypeError}}, and abort these
-                steps.
-                
-              
+            If [=validate share data=] with |data| and |base| returns
+            false, then return [=a promise rejected with=] a {{TypeError}}.
             
             If |data|'s {{ShareData/url}} member is present:
               
-                Let |base:URL| be the [=this=] value's relevant settings
-                object's [=environment settings object/api base URL=].
-                
                 Let |url:URL| be the result of running the URL
                 parser on |data|'s {{ShareData/url}} with |base|.
                 
-                If |url| is failure, return a promise rejected with
-                {{TypeError}}.
-                
-                If |url|'s [=URL/scheme=] is not "http" or "https", return
-                a promise rejected with {{TypeError}}.
+                Assert: |url| is {{URL}}.
                 
                 Set |data| to a copy of |data|, with its {{ShareData/url}}
                 member set to the result of running the URL serializer
@@ -271,6 +257,65 @@ 
             or bypassing the UI if there is only a single share target.
           
         
+        
+          
+            Validate share data
+          
+          
+            To validate share data with |data:ShareData| and
+            |base:URL|, run the following steps:
+          
+          
+            If none of |data|'s members {{ShareData/title}},
+            {{ShareData/text}}, or {{ShareData/url}} or {{ShareData/files}} are
+            present, return false.
+            
+            Let |titleTextOrUrl:boolean| be true if any of
+            {{ShareData/title}}, or {{ShareData/text}}, or {{ShareData/url}} is
+            present.
+            
+            If |data|'s {{ShareData/files}} member is present:
+              
+                If |titleTextOrUrl| is false and |data|'s
+                {{ShareData/files}} member is empty, return false.
+                  
+                    This causes a `{ files: [] }` dictionary to be treated as
+                    an empty dictionary. However, passing a dictionary like
+                    `{text: "text", files: []}` is fine, as `files` is just
+                    ignored.
+                  
+                
+                If the implementation does not support file sharing, return
+                false.
+                
+                If the user agent believes sharing any of the files in
+                `files` would result in a potentially hostile share, return
+                false.
+                
+              
+            
+            If |data|'s {{ShareData/url}} member is present:
+              
+                Let |url:URL| be the result of running the [=URL parser=]
+                on |data|'s {{ShareData/url}} member, with |base|, and no
+                encoding override.
+                
+                If |url| is failure, return false.
+                
+                
+                  
+                    If |url| is a URL the user agent deems potentially hostile
+                    (e.g., "file:") or wouldn't make sense to outside the scope
+                    of the document (e.g., "blob:"), return false.
+                  
+                  
+                
+              
+            
+            Return true.
+            
+          
+