Introduce WebRequestResourceType.

extensions/browser/api/web_request/web_request_resource_type.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef EXTENSIONS_BROWSER_API_WEB_REQUEST_WEB_REQUEST_RESOURCE_TYPE_H_
+#define EXTENSIONS_BROWSER_API_WEB_REQUEST_WEB_REQUEST_RESOURCE_TYPE_H_
+
+#include "content/public/common/resource_type.h"
+
+namespace extensions {
+
+// Enumerates all resource/request types that WebRequest API cares about.
+enum class WebRequestResourceType {
+  // Below are content::ResourceType values. Note: Each content::RESOURCE_TYPE_*
+  // is typed explicitly in order to catch if some of those values get deleted.
+  MAIN_FRAME = content::RESOURCE_TYPE_MAIN_FRAME,
+  SUB_FRAME = content::RESOURCE_TYPE_SUB_FRAME,
+  STYLESHEET = content::RESOURCE_TYPE_STYLESHEET,
+  SCRIPT = content::RESOURCE_TYPE_SCRIPT,
+  IMAGE = content::RESOURCE_TYPE_IMAGE,
+  FONT_RESOURCE = content::RESOURCE_TYPE_FONT_RESOURCE,
+  SUB_RESOURCE = content::RESOURCE_TYPE_SUB_RESOURCE,
+  OBJECT = content::RESOURCE_TYPE_OBJECT,
+  MEDIA = content::RESOURCE_TYPE_MEDIA,
+  WORKER = content::RESOURCE_TYPE_WORKER,
+  SHARED_WORKER = content::RESOURCE_TYPE_SHARED_WORKER,
+  PREFETCH = content::RESOURCE_TYPE_PREFETCH,
+  FAVICON = content::RESOURCE_TYPE_FAVICON,
+  XHR = content::RESOURCE_TYPE_XHR,
+  PING = content::RESOURCE_TYPE_PING,
+  SERVICE_WORKER = content::RESOURCE_TYPE_SERVICE_WORKER,
+  CSP_REPORT = content::RESOURCE_TYPE_CSP_REPORT,
+  PLUGIN_RESOURCE = content::RESOURCE_TYPE_PLUGIN_RESOURCE,
+
+  // Types of requests not in content::ResourceType.
+  WEBSOCKET,
+
+  LAST_TYPE,
+};
+
+static_assert(content::RESOURCE_TYPE_LAST_TYPE ==
+                  content::RESOURCE_TYPE_PLUGIN_RESOURCE + 1,
+              "content::ResourceType has been modified.");

[tyoshino (SeeGerritForStatus), 2017/02/16 16:13:58]

The comment for ResourceType is saying:

// Used in histograms; explicitly assign each type and do not re-use old values.

Strictly speaking, this doesn't guarantee that new value is never added between
existing ones. Then, this static_assert cannot capture such a change.

Ideally, I'd like to have an assert that doesn't depend on this assumption. But,
comparing RESOURCE_TYPE_LAST_TYPE with the first element we add here (currently
WebRequestResourceType::WEBSOCKET) still doesn't work. Hmm, I don't come up with
any simple solution that can capture such a change.

But, given that this can at least capture next addition of new ResourceType and
there's no gap in ResourceType at this point, it's too much to worry about that
now.

So, ok.

[pkalinnikov, 2017/02/16 19:27:30]

Ack. This is approximately what I thought here as well :)

After my last changes this is not a problem any more.

+
+inline WebRequestResourceType ToWebRequestResourceType(
+    content::ResourceType type) {
+  return type == content::RESOURCE_TYPE_LAST_TYPE
+             ? WebRequestResourceType::LAST_TYPE
+             : static_cast<WebRequestResourceType>(type);
+}
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_WEB_REQUEST_WEB_REQUEST_RESOURCE_TYPE_H_