Bind ModelLoader to a sequence, not a thread.

chrome/browser/safe_browsing/client_side_model_loader.h

 // Copyright (c) 2012 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.
 //
 // Helper class loads models for client-side phishing detection
 // from the the SafeBrowsing backends.
-//
-// This class is not thread-safe and expects all calls to be made on the UI
-// thread.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_CLIENT_SIDE_MODEL_LOADER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_CLIENT_SIDE_MODEL_LOADER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "content/public/browser/browser_thread.h"
+#include "base/sequence_checker.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "url/gurl.h"
 
 namespace base {
 class TimeDelta;
 }
 
 namespace net {
 class URLFetcher;
 class URLRequestContextGetter;
 }  // namespace net
 
 namespace safe_browsing {
 class ClientSideModel;
 
 // Class which owns and loads a single client-Side detection model.
 // The ClientSideDetectionService uses this.
 class ModelLoader : public net::URLFetcherDelegate {
  public:
   static const size_t kMaxModelSizeBytes;
   static const int kClientModelFetchIntervalMs;
   static const char kClientModelFinchExperiment[];
   static const char kClientModelFinchParam[];
   static const char kClientModelUrlPrefix[];
   static const char kClientModelNamePattern[];
 
+  // Construct a model loader to fetch a model using |request_context_getter|.
+  // When ScheduleFetch is called, |update_renderers| will be called on the
+  // same sequence if the fetch is successful.
   ModelLoader(base::Closure update_renderers,
               net::URLRequestContextGetter* request_context_getter,
               bool is_extended_reporting);
   ~ModelLoader() override;
 
   // From the net::URLFetcherDelegate interface.
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
   // Schedules the next fetch of the model.
   virtual void ScheduleFetch(int64_t delay_ms);
 
-  // Cancel any pending model fetch.
+  // Cancel any pending model fetch. This must be called from the same sequence
+  // as ScheduleFetch.
   virtual void CancelFetcher();
 
   const std::string& model_str() const { return model_str_; }
   const std::string& name() const { return name_; }
 
  protected:
   // Enum used to keep stats about why we fail to get the client model.
   enum ClientModelStatus {
     MODEL_SUCCESS,
     MODEL_NOT_CHANGED,
@@ skipping 14 matching lines @@
   // available for download.
   virtual void StartFetch();
 
   // This method is called when we're done fetching the model either because
   // we hit an error somewhere or because we're actually done fetch and
   // validating the model.  If |max_age| is not 0, it's used to schedule the
   // next fetch.
   virtual void EndFetch(ClientModelStatus status, base::TimeDelta max_age);
 
  private:
+  // Common constructor called from both the public and test-only constructors.
+  ModelLoader(base::Closure update_renderers,
+              net::URLRequestContextGetter* request_context_getter,
+              const std::string& model_name);
+
   // Use Finch to pick a model number.
   static int GetModelNumber();
 
   // Construct a model name from parameters.
   static std::string FillInModelName(bool is_extended_reporting,
                                      int model_number);
 
   // Returns true iff all the hash id's in the client-side model point to
   // valid hashes in the model.
   static bool ModelHasValidHashIds(const ClientSideModel& model);
@@ skipping 10 matching lines @@
 
   // Callback to invoke when we've got a new model.  CSD will send it around.
   base::Closure update_renderers_callback_;
 
   // Not owned, must outlive this obj or be NULL.
   net::URLRequestContextGetter* request_context_getter_;
 
   // Used to protect the delayed callback to StartFetchModel()
   base::WeakPtrFactory<ModelLoader> weak_factory_;
 
+  // Used to check that ScheduleFetch and CancelFetcher are called on the same
+  // sequence.
+  base::SequenceChecker fetch_sequence_checker_;
+
   friend class ClientSideDetectionServiceTest;
   friend class ModelLoaderTest;
   FRIEND_TEST_ALL_PREFIXES(ModelLoaderTest, FetchModelTest);
   FRIEND_TEST_ALL_PREFIXES(ModelLoaderTest, ModelHasValidHashIds);
   FRIEND_TEST_ALL_PREFIXES(ModelLoaderTest, ModelNamesTest);
   FRIEND_TEST_ALL_PREFIXES(ModelLoaderTest, RescheduleFetchTest);
   FRIEND_TEST_ALL_PREFIXES(ModelLoaderTest, UpdateRenderersTest);
   FRIEND_TEST_ALL_PREFIXES(ClientSideDetectionServiceTest,
                            SetEnabledAndRefreshState);
   DISALLOW_COPY_AND_ASSIGN(ModelLoader);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_CLIENT_SIDE_MODEL_LOADER_H_