Don't start a second pre-render if one is in progress.

components/offline_pages/background/request_coordinator_unittest.cc

Index: components/offline_pages/background/request_coordinator_unittest.cc
diff --git a/components/offline_pages/background/request_coordinator_unittest.cc b/components/offline_pages/background/request_coordinator_unittest.cc
index ebcbe140f39a7b3f1a30b8ffbf8e619d52ed20f4..0953dd61dc9277640a1165b793ddd8b2682410ab 100644
--- a/components/offline_pages/background/request_coordinator_unittest.cc
+++ b/components/offline_pages/background/request_coordinator_unittest.cc
@@ -10,6 +10,7 @@
 
 #include "base/bind.h"
 #include "base/location.h"
+#include "base/logging.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/offline_pages/background/device_conditions.h"
@@ -54,23 +55,37 @@ class SchedulerStub : public Scheduler {
 };
 
 class OfflinerStub : public Offliner {
+ public:
+  OfflinerStub() : skip_callback_(false) {}
+
   bool LoadAndSave(const SavePageRequest& request,
                    const CompletionCallback& callback) override {
     // Post the callback on the run loop.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
-        FROM_HERE,
-        base::Bind(callback, request, Offliner::RequestStatus::SAVED));
+    if (!skip_callback_) {
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE,
+          base::Bind(callback, request, Offliner::RequestStatus::SAVED));
+    }
     return true;
   }
 
   // Clears the currently processing request, if any.
   void Cancel() override {}
+
+  void set_skip_callback(bool skip) {
+    skip_callback_ = skip;
+  }
+
+ private:
+  bool skip_callback_;
 };
 
 class OfflinerFactoryStub : public OfflinerFactory {
  public:
   Offliner* GetOffliner(const OfflinerPolicy* policy) override {
-    offliner_.reset(new OfflinerStub());
+    if (offliner_.get() == nullptr) {
+      offliner_.reset(new OfflinerStub());
+    }
     return offliner_.get();
   }
 
@@ -92,6 +107,14 @@ class RequestCoordinatorTest
     return coordinator_.get();
   }
 
+  bool is_busy() {
+    return coordinator_->is_busy();
+  }
+
+  void SendRequestToOffliner(SavePageRequest& request) {
+    coordinator_->SendRequestToOffliner(request);
+  }
+
   // Empty callback function
   void EmptyCallbackFunction(bool result) {
   }
@@ -115,24 +138,32 @@ class RequestCoordinatorTest
     return last_requests_;
   }
 
+  void skip_offliner_callback() {
+    offliner_->set_skip_callback(true);
+  }
+
  private:
   RequestQueue::GetRequestsResult last_get_requests_result_;
   std::vector<SavePageRequest> last_requests_;
   scoped_refptr<base::TestSimpleTaskRunner> task_runner_;
   base::ThreadTaskRunnerHandle task_runner_handle_;
   std::unique_ptr<RequestCoordinator> coordinator_;
+  OfflinerStub* offliner_;
 };
 
 RequestCoordinatorTest::RequestCoordinatorTest()
     : last_get_requests_result_(RequestQueue::GetRequestsResult::STORE_FAILURE),
       task_runner_(new base::TestSimpleTaskRunner),
-      task_runner_handle_(task_runner_) {}
+      task_runner_handle_(task_runner_),
+      offliner_(nullptr) {}
 
 RequestCoordinatorTest::~RequestCoordinatorTest() {}
 
 void RequestCoordinatorTest::SetUp() {
   std::unique_ptr<OfflinerPolicy> policy(new OfflinerPolicy());
   std::unique_ptr<OfflinerFactory> factory(new OfflinerFactoryStub());
+  offliner_ =
+      reinterpret_cast<OfflinerStub*>(factory->GetOffliner(policy.get()));
   std::unique_ptr<RequestQueueInMemoryStore>
       store(new RequestQueueInMemoryStore());
   std::unique_ptr<RequestQueue> queue(new RequestQueue(std::move(store)));
@@ -175,6 +206,30 @@ TEST_F(RequestCoordinatorTest, StartProcessingWithNoRequests) {
   EXPECT_TRUE(coordinator()->StartProcessing(device_conditions, callback));
 }
 
+TEST_F(RequestCoordinatorTest, StartProcessingWithRequestInProgress) {
+  // Put the request on the queue.
+  EXPECT_TRUE(coordinator()->SavePageLater(kUrl, kClientId));
+
+  // Set up for the call to StartProcessing by building arguments.
+  DeviceConditions device_conditions(false, 75,
+                                     net::NetworkChangeNotifier::CONNECTION_3G);
+  base::Callback<void(bool)> callback =
+      base::Bind(&RequestCoordinatorTest::EmptyCallbackFunction,
+                 base::Unretained(this));
+
+  // Ensure that the forthcoming request does not finish - we simulate it being
+  // in progress by asking it to skip making the completion callback.
+  skip_offliner_callback();
+
+  // Sending the request to the offliner should make it busy.
+  EXPECT_TRUE(coordinator()->StartProcessing(device_conditions, callback));
+  PumpLoop();
+  EXPECT_TRUE(is_busy());
+
+  // Now trying to start processing on another request should return false.
+  EXPECT_FALSE(coordinator()->StartProcessing(device_conditions, callback));
+}
+
 TEST_F(RequestCoordinatorTest, SavePageLater) {
   EXPECT_TRUE(coordinator()->SavePageLater(kUrl, kClientId));