Update from https://crrev.com/304121

cc/resources/rasterizer.h

Index: cc/resources/rasterizer.h
diff --git a/cc/resources/rasterizer.h b/cc/resources/rasterizer.h
index 526058c338d01d42ef7fcb56b587f648c8103537..db84c2223eba9566a2b7e5218b3bef8762cceafe 100644
--- a/cc/resources/rasterizer.h
+++ b/cc/resources/rasterizer.h
@@ -87,7 +87,11 @@ class CC_EXPORT RasterTask : public RasterizerTask {
   ImageDecodeTask::Vector dependencies_;
 };
 
-static const size_t kNumberOfTaskSets = 2;
+// kNumberOfTaskSets must be greater or equal to the number of values in
+// TileManager::NamedTaskSet.
+// TODO(reveman): Use template specialization to make it easy for client code to
+// check at compile time that the number of supported task sets is correct.
+static const size_t kNumberOfTaskSets = 3;
 typedef size_t TaskSet;
 typedef std::bitset<kNumberOfTaskSets> TaskSetCollection;