Add the ability to cancel prerender reqeusts and tests

components/offline_pages/background/request_coordinator.h

Index: components/offline_pages/background/request_coordinator.h
diff --git a/components/offline_pages/background/request_coordinator.h b/components/offline_pages/background/request_coordinator.h
index d04ba515fa9f00c1a7fbfb41365a4431db9924a5..8545db844bc22022bd13b824982903180148c21c 100644
--- a/components/offline_pages/background/request_coordinator.h
+++ b/components/offline_pages/background/request_coordinator.h
@@ -81,6 +81,10 @@ class RequestCoordinator : public KeyedService {
     return is_busy_;
   }
 
+  bool is_canceled() {

[dougarnett, 2016/06/23 17:19:17]

or maybe was_canceled?

[dougarnett, 2016/06/23 17:19:17]

// Tracks whether processing has been canceled. Reset upon next StartProcessing
call.   ?

[Pete Williamson, 2016/06/23 17:54:53]

Done.

[Pete Williamson, 2016/06/23 17:54:54]

I thought that is_canceled would work better with is_busy, and to me the state
of cancellation seems to be ongoing until we actually cancel it, so I prefer
is_canceled.  What do you think?

+    return is_canceled_;
+  }
+
  private:
   void AddRequestResultCallback(RequestQueue::AddRequestResult result,
                                 const SavePageRequest& request);
@@ -102,12 +106,18 @@ class RequestCoordinator : public KeyedService {
 
   void TryNextRequest();
 
+  void GetOffliner();

[dougarnett, 2016/06/23 17:19:17]

// Returns the appropriate Offliner to use.  ?

[Pete Williamson, 2016/06/23 17:54:53]

The real purpose of this is not choosing the offliner, but getting one  from the
factory if needed.  Comment now says both.

+
   friend class RequestCoordinatorTest;
 
   // The offliner can only handle one request at a time - if the offliner is
   // busy, prevent other requests.  This flag marks whether the offliner is in
   // use.
   bool is_busy_;
+  // True if a prerender request has been canceled.
+  bool is_canceled_;
+  // Unowned pointer to the offliner, if any.

[dougarnett, 2016/06/23 17:19:17]

to the current offliner ?

[Pete Williamson, 2016/06/23 17:54:53]

Done.

+  Offliner* offliner_;
   // RequestCoordinator takes over ownership of the policy
   std::unique_ptr<OfflinerPolicy> policy_;
   // OfflinerFactory.  Used to create offline pages. Owned.