Re-land: cc: Add raster finished signals to RasterWorkerPool.

cc/resources/raster_worker_pool_unittest.cc

Index: cc/resources/raster_worker_pool_unittest.cc
diff --git a/cc/resources/raster_worker_pool_unittest.cc b/cc/resources/raster_worker_pool_unittest.cc
index ed98e48340f5a5c36c8fc97f3305a05aa2b63ac1..d507d2000583eaeb508c0e8e4d5c866f09e7e976 100644
--- a/cc/resources/raster_worker_pool_unittest.cc
+++ b/cc/resources/raster_worker_pool_unittest.cc
@@ -78,6 +78,8 @@ class RasterWorkerPoolTest : public testing::Test,
       OVERRIDE {
     return false;
   }
+  virtual void DidFinishedRunningTasks() OVERRIDE { }
+  virtual void DidFinishedRunningTasksRequiredForActivation() OVERRIDE {}
 
   virtual void BeginTest() = 0;
   virtual void AfterTest() = 0;