Add some tests for ThrottlingResourceHandler.

content/browser/loader/mock_resource_loader.h

+// Copyright 2016 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 CONTENT_BROWSER_LOADER_MOCK_RESOURCE_LOADER_H_
+#define CONTENT_BROWSER_LOADER_MOCK_RESOURCE_LOADER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "content/browser/loader/resource_controller.h"
+#include "net/base/net_errors.h"
+
+class GURL;
+
+namespace net {
+struct RedirectInfo;
+class URLRequestStatus;
+}
+
+namespace content {
+class ResourceHandler;
+struct ResourceResponse;
+
+// Class that takes the place of the ResourceLoader for tests. It simplifies
+// testing ResourceHandlers by managing callbacks and performing basic sanity
+// checks. The test fixture is responsible for advancing states.
+class MockResourceLoader : public ResourceController {
+ public:
+  explicit MockResourceLoader(ResourceHandler* resource_handler);
+  ~MockResourceLoader() override;
+
+  // Idle means the ResourceHandler is waiting for the next call from the
+  // TestFixture/ResourceLoader, CALLBACK_PENDING means that the ResourceHandler
+  // will resume the request at some future point to resume the request, and
+  // CANCELED means the ResourceHandler cancelled the request.
+  enum class Status {
+    // The MockLoader is waiting for more data from hte test fixture.
+    IDLE,
+    // The MockLoader is currently in the middle of a call to a handler. Will
+    // switch to CALLBACK_PENDING if the handler defers handling the request.
+    CALLING_HANDLER,
+    // The MockLoader is waiting for a callback from the ResourceHandler.
+    CALLBACK_PENDING,
+    // The request was cancelled.
+    CANCELED,
+  };
+
+  // These all run the corresponding methods on ResourceHandler, along with
+  // basic sanity checks for the behavior of the handler. Each check returns the
+  // current status of the ResourceLoader.
+  Status OnWillStart(const GURL& url);
+  Status OnRequestRedirected(const net::RedirectInfo& redirect_info,
+                             ResourceResponse* response);
+  Status OnResponseStarted(ResourceResponse* response);
+  Status OnWillRead(int min_size);
+  Status OnReadCompleted(int bytes_read);
+  Status OnResponseCompleted(const net::URLRequestStatus& status);
+
+  Status status() const { return status_; }
+
+  // Network error passed to the first CancelWithError() / Cancel() call, which
+  // is the one the real code uses in the case of multiple cancels.
+  int error_code() const { return error_code_; }
+
+ private:
+  // ResourceController implementation.
+  void Cancel() override;
+  void CancelAndIgnore() override;
+  void CancelWithError(int error_code) override;
+  void Resume() override;
+
+  ResourceHandler* const resource_handler_;
+
+  Status status_ = Status::IDLE;
+  int error_code_ = net::OK;
+
+  DISALLOW_COPY_AND_ASSIGN(MockResourceLoader);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_TEST_RESOURCE_HANDLER_WRAPPER_H_