Create image cache for use by json canvas

tools/UrlDataManager.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "UrlDataManager.h"
+
+bool operator==(const SkData& a, const SkData& b) {
+    return a.equals(&b);
+}
+
+UrlDataManager::UrlDataManager(SkString rootUrl) : fRootUrl(rootUrl), fDataId(0) {}
+
+SkString UrlDataManager::addData(SkData* data, const char* contentType) {
+    UrlData* urlData = fCache.find(*data);
+    if (fCache.find(*data)) {
+        SkASSERT(data->equals(urlData->fData.get()));
+        return urlData->fUrl;
+    }
+
+    urlData = new UrlData;
+    urlData->fData.reset(SkRef(data));
+    urlData->fContentType.set(contentType);
+    urlData->fUrl.appendf("%s/%d", fRootUrl.c_str(), fDataId++);
+
+    fCache.add(urlData);
+
+    SkASSERT(!fUrlLookup.find(urlData->fUrl));
+    fUrlLookup.add(urlData);
+    return urlData->fUrl;
+}
+
+void UrlDataManager::reset() {
+    SkTDynamicHash<UrlData, SkData, LookupTrait>::Iter iter(&fCache);
+    while (!iter.done()) {
+        UrlData* urlData = &(*iter);
+        urlData->unref();
+        ++iter;
+    }
+
+    fCache.rewind();
+}