feat: disable cookie access under restricted sandboxes

When dash is embedded into an iframe with a sandbox attribute that only has allow-scripts, cookie access is disabled and dash fails to load. As such, we need to restrict our cookie usage by disabling functionality.

This patch removes the disabled functionality in a graceful manner, allowing dash to load in very restricted iframes.

dash-renderer/src/AccessDenied.react.js

@@ -28,9 +28,12 @@ function AccessDenied(props) {
             <a
                 style={styles.base.a}
                 onClick={() => {
-                    document.cookie =
-                        `${constants.OAUTH_COOKIE_NAME}=; ` +
-                        'expires=Thu, 01 Jan 1970 00:00:01 GMT;';
+                    /* eslint no-empty: ["error", { "allowEmptyCatch": true }] */
+                    try {
+                        document.cookie =
+                            `${constants.OAUTH_COOKIE_NAME}=; ` +
+                            'expires=Thu, 01 Jan 1970 00:00:01 GMT;';
+                    } catch (e) {}
                     window.location.reload(true);
                 }}
             >

dash-renderer/src/actions/index.js

@@ -55,9 +55,13 @@ export function hydrateInitialOutputs() {
 }
 
 export function getCSRFHeader() {
-    return {
-        'X-CSRFToken': cookie.parse(document.cookie)._csrf_token,
-    };
+    try {
+        return {
+            'X-CSRFToken': cookie.parse(document.cookie)._csrf_token,
+        };
+    } catch (e) {
+        return {};
+    }
 }
 
 function triggerDefaultState(dispatch, getState) {