Define concepts for converting and validating .data (#977)

This makes it easier for other specifications to clearly indicate their defined
steps to convert and validate the data member.

Author: stephenmcgruer

index.html

@@ -148,6 +148,31 @@ 
         method.
         li>
       ul>
+      <p>
+        A payment method defines:
+      p>
+      <dl>
+        <dt>
+          An optional <dfn data-dfn-for="Payment Method">additional data typedfn>
+        dt>
+        <dd>
+          Optionally, an IDL type that the <a>payment methoda> expects
+          to receive as the {{PaymentMethodData}}'s {{PaymentMethodData/data}}
+          member. If not specified for a given payment method, no conversion to
+          IDL is done and the payment method will receive
+          {{PaymentMethodData/data}} as JSON.
+        dd>
+        <dt>
+          <dfn>Steps to validate payment method datadfn>
+        dt>
+        <dd>
+          Algorithmic steps that specify how a <a>payment methoda> validates
+          the {{PaymentMethodData/data}} member of the {{PaymentMethodData}},
+          after it is converted to the payment method's
+          [=Payment Method/additional data type=]. If not specified for a given
+          payment method, no validation is done.
+        dd>
+      dl>
       <p>
         The details of how to fulfill a payment request for a given <a>payment
         methoda> is an implementation detail of a <dfn data-export="">payment
@@ -573,9 +598,10 @@ 
                   |paymentMethod|.{{PaymentMethodData/data}} into a string.
                   Rethrow any exceptions.
                   li>
-                  <li>If |serializedData| is not null, and if required by the
-                  specification that defines the
-                  |paymentMethod|.{{PaymentMethodData/supportedMethods}}:
+                  <li>If |serializedData| is not null, and if the specification
+                  that defines the
+                  |paymentMethod|.{{PaymentMethodData/supportedMethods}}
+                  specifies an [=Payment Method/additional data type=]:
                     <ol>
                       <li>Let |object| be the result of <a data-cite=
                       "ECMASCRIPT#sec-json.parse">JSON-parsinga>
@@ -585,15 +611,16 @@ 
                         <p>
                           Let |idl| be the result of [=converted to an IDL
                           value|converting=] |object| to an IDL value of the
-                          type specified by the specification that defines the
-                          |paymentMethod|.{{PaymentMethodData/supportedMethods}}.
-                          Rethrow any exceptions.
+                          [=Payment Method/additional data type=]. Rethrow any
+                          exceptions.
                         p>
+                      li>
+                      <li>
                         <p>
-                          If required by the specification that defines the
-                          |paymentMethod|.{{PaymentMethodData/supportedMethods}},
-                          validate the members of |idl|. If a member's value is
-                          invalid, throw a {{TypeError}}.
+                          Run the <a>steps to validate payment method dataa>,
+                          if any, from the specification that defines the
+                          |paymentMethod|.{{PaymentMethodData/supportedMethods}}
+                          on |object|. Rethrow any exceptions.
                         p>
                         <p class="note">
                           These step assures that any IDL type conversion and
@@ -855,10 +882,11 @@ 
               "ECMASCRIPT#sec-json.parse">JSON-parsinga> the second element
               in the |paymentMethod| tuple.
               li>
-              <li>If required by the specification that defines the
-              |identifier|, then [=converted to an IDL value|convert=] |data|
-              to an IDL value of the type specified there. Otherwise,
-              [=converted to an IDL value|convert=] to {{object}}.
+              <li>If the specification that defines the |identifier| specifies
+              an [=Payment Method/additional data type=], then [=converted to an
+              IDL value|convert=] |data| to an IDL value of that type.
+              Otherwise, [=converted to an IDL value|convert=] |data| to
+              {{object}}.
               li>
               <li>If conversion results in an <a>exceptiona> |error|:
                 <ol>