Refactor net::BackoffEntry to not require subclassing

components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
index 105ac2a237c419f9ce66d44ce1ed100949b09fc8..8d2cf29f5e3596405e44e40894f95012ca50d3d4 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
@@ -11,6 +11,8 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/single_thread_task_runner.h"
+#include "base/time/clock.h"
+#include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_stats.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h"
@@ -114,15 +116,15 @@ class TestDataReductionProxyConfigServiceClient
 
  private:
   // A clock which returns a fixed value in both base::Time and base::TimeTicks.
-  class TestTickClock {
+  class TestTickClock : public base::Clock, public base::TickClock {
    public:
     TestTickClock(const base::Time& initial_time);
 
-    // Returns the current base::TimeTicks
-    base::TimeTicks NowTicks() const;
+    // base::TickClock implementation.
+    base::TimeTicks NowTicks() override;
 
-    // Returns the current base::Time
-    base::Time Now() const;
+    // base::Clock implementation.
+    base::Time Now() override;
 
     // Sets the current time.
     void SetTime(const base::Time& time);
@@ -131,23 +133,8 @@ class TestDataReductionProxyConfigServiceClient
     base::Time time_;
   };
 
-  // A net::BackoffEntry which uses an injected base::TickClock to control
-  // the backoff expiration time.
-  class TestBackoffEntry : public net::BackoffEntry {
-   public:
-    TestBackoffEntry(const BackoffEntry::Policy* const policy,
-                     const TestTickClock* tick_clock);
-
-   protected:
-    // Override of net::BackoffEntry.
-    base::TimeTicks ImplGetTimeNow() const override;
-
-   private:
-    const TestTickClock* tick_clock_;
-  };
-
-  TestTickClock tick_clock_;
-  TestBackoffEntry test_backoff_entry_;
+  mutable TestTickClock tick_clock_;

[mmenke, 2015/04/10 15:50:43]

Why does this have to be mutable?

[johnme, 2015/04/10 16:23:36]

It was because base::Clock::Now is non-const, hence TestTickClock::Now must be
non-const, but TestDataReductionProxyConfigServiceClient::Now must be const
since DataReductionProxyConfigServiceClient::Now is const.

I've made TestTickClock no longer inherit from base::Clock (I only added that
for symmetry), so Now can be const again and it no longer needs to be mutable.
However this is now a little asymmetric, with one method const and the other
non-const :-|

Alternatively, if you'd rather, I could make
DataReductionProxyConfigServiceClient::Now be non-const, as it's never currently
used in a const manner?

[mmenke, 2015/04/10 16:26:37]

I'd go ahead and make DataReductionProxyConfigServiceClient::Now non-const, for
simplicity, but don't have strong feelings on the subject.

+  net::BackoffEntry test_backoff_entry_;
 };
 
 // Test version of |DataReductionProxyService|, which permits mocking of various