Make it possible to clear the cache, used by the getB function in src/core/pattern.js

While this cache will not contain a huge amount of data in practice, it's nonetheless a *global* cache that currently will never be cleared.

This patch also removes the existing closure, since it shouldn't really be necessary nowadays given that the code is a JavaScript module which means that only explicitly listed properties will be exported.

src/core/cleanup_helper.js

@@ -13,10 +13,12 @@
  * limitations under the License.
  */
 
+import { clearPatternCaches } from "./pattern.js";
 import { clearPrimitiveCaches } from "./primitives.js";
 import { clearUnicodeCaches } from "./unicode.js";
 
 function clearGlobalCaches() {
+  clearPatternCaches();
   clearPrimitiveCaches();
   clearUnicodeCaches();
 }

src/core/pattern.js

@@ -411,8 +411,9 @@ class MeshStreamReader {
   }
 }
 
-const getB = (function getBClosure() {
+let bCache = Object.create(null);
-  function buildB(count) {
+
+function buildB(count) {
   const lut = [];
   for (let i = 0; i <= count; i++) {
     const t = i / count,
@@ -422,13 +423,14 @@ const getB = (function getBClosure() {
     );
   }
   return lut;
-  }
+}
-  const cache = Object.create(null);
+function getB(count) {
+  return (bCache[count] ||= buildB(count));
+}
 
-  return function (count) {
+function clearPatternCaches() {
-    return (cache[count] ||= buildB(count));
+  bCache = Object.create(null);
-  };
+}
-})();
 
 class MeshShading extends BaseShading {
   static MIN_SPLIT_PATCH_CHUNKS_AMOUNT = 3;
@@ -1000,4 +1002,4 @@ function getTilingPatternIR(operatorList, dict, color) {
   ];
 }
 
-export { getTilingPatternIR, Pattern };
+export { clearPatternCaches, getTilingPatternIR, Pattern };