Expand consent string size limit to 1024 (#28400)

* expand consent string size limit to 1024

* update doc

extensions/amp-consent/0.1/consent-state-manager.js

@@ -35,7 +35,7 @@ const TAG = 'CONSENT-STATE-MANAGER';
 const CID_SCOPE = 'AMP-CONSENT';
 
 /** @visibleForTesting */
-export const CONSENT_STRING_MAX_LENGTH = 200;
+export const CONSENT_STRING_MAX_LENGTH = 1024;
 
 export class ConsentStateManager {
  /**
@@ -377,8 +377,7 @@ export class ConsentInstance {
  const consentStr = consentInfo['consentString'];
  if (consentStr && consentStr.length > CONSENT_STRING_MAX_LENGTH) {
  // Verify the length of consentString.
- // 200 * 2 (utf8Encode) * 4/3 (base64) = 533 bytes.
- // TODO: Need utf8Encode if necessary.
+ // 1024 * 4/3 (base64) = 1336 bytes.
  user().error(
  TAG,
  'Cannot store consentString which length exceeds %s. ' +

extensions/amp-consent/integrating-consent.md

@@ -14,7 +14,7 @@ To add your consent management service to AMP runtime, it is expected that you:
 - Meet the restrictions that the AMP runtime applies to ensure a good user experience. These includes
  - Enforce the size of the consent prompt. The only two allowed sizes are the initial size (`width: 100vw`, `height: 30vh`), and the full screen size (`width: 100vw`, `height: 100%`) after user interactions.
  - A default placeholder will be displayed before the consent prompt iframe is ready.
- - Enforce the size of the stored consent information. 200 character length is the current limit. Please [file an issue](https://github.com/ampproject/amphtml/issues/new) if you find that not sufficient.
+ - Enforce the size of the stored consent information. 1024 character length is the limit. Please [file an issue](https://github.com/ampproject/amphtml/issues/new) if you find that not sufficient.
 - Understand that including `<amp-consent type='yourName'></amp-consent>` on the page won't block any components by default. **Please make sure to inform your service users to block AMP components either by the `<meta name="amp-consent-blocking">` metaTag, or the `data-block-on-consent` attribute.**
 - Understand that AMP Consent doesn't attempt to interpret the consent info string from the CMP. Vendors can access the consent info string from CMPs via [provided APIs](https://github.com/ampproject/amphtml/blob/master/ads/README.md#amp-consent-integration). It's up to the CMP and service provider vendors to agree on the format of the consent info string.
 - Create an [Intent-To-Implement issue](../../CONTRIBUTING.md#contributing-features) stating that you'll be adding support to your CMP service to AMP. A great start point is to follow the `_ping_` CMP service implementation that the AMP team creates for testing purpose.