1 files changed, 52 insertions, 0 deletions
diff --git a/catapult/third_party/polymer/components/shadycss/src/style-cache.js b/catapult/third_party/polymer/components/shadycss/src/style-cache.js
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index 00000000..0006a0bc
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+++ b/catapult/third_party/polymer/components/shadycss/src/style-cache.js
@@ -0,0 +1,52 @@
+/**
+@license
+Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+*/
+'use strict';
+
+export default class StyleCache {
+  constructor(typeMax = 100) {
+    // map element name -> [{properties, styleElement, scopeSelector}]
+    this.cache = {};
+    /** @type {number} */
+    this.typeMax = typeMax;
+  }
+
+  _validate(cacheEntry, properties, ownPropertyNames) {
+    for (let idx = 0; idx < ownPropertyNames.length; idx++) {
+      let pn = ownPropertyNames[idx];
+      if (cacheEntry.properties[pn] !== properties[pn]) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  store(tagname, properties, styleElement, scopeSelector) {
+    let list = this.cache[tagname] || [];
+    list.push({properties, styleElement, scopeSelector});
+    if (list.length > this.typeMax) {
+      list.shift();
+    }
+    this.cache[tagname] = list;
+  }
+
+  fetch(tagname, properties, ownPropertyNames) {
+    let list = this.cache[tagname];
+    if (!list) {
+      return;
+    }
+    // reverse list for most-recent lookups
+    for (let idx = list.length - 1; idx >= 0; idx--) {
+      let entry = list[idx];
+      if (this._validate(entry, properties, ownPropertyNames)) {
+        return entry;
+      }
+    }
+  }
+}