cc: Only make num_threads - 1 SkPicture clones.

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 82befc7438141c0cf7eadccfed2d374a3c025782..f0a1b5e1bc156f85ea3e46e1837f5eefa5bb6322 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -19,6 +19,8 @@
 #include "cc/quads/solid_color_draw_quad.h"
 #include "cc/quads/tile_draw_quad.h"
 #include "cc/quads/yuv_video_draw_quad.h"
+#include "cc/resources/raster_worker_pool.h"
+#include "cc/resources/task_graph_runner.h"
 #include "ui/gfx/quad_f.h"
 
 class SkBitmap;
@@ -428,6 +430,7 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
 
   SkBitmap on_demand_tile_raster_bitmap_;
   ResourceProvider::ResourceId on_demand_tile_raster_resource_id_;
+  internal::NamespaceToken on_demand_task_namespace_;
 
   DISALLOW_COPY_AND_ASSIGN(GLRenderer);
 };