Remove image_decode_tasks_enabled flag.

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 3e24319ca20fe4639a81ac8c73ebdba24b16e1ce..862bc1b92a5dac1b389f279c3dbf0317ad1ca82a 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -186,11 +186,6 @@ Compositor::Compositor(const cc::FrameSinkId& frame_sink_id,
     }
   }
 
-  // Note: Although there is only one image decode thread, we should still get a
-  // benefit from locking images across several raster tasks. At worst, this
-  // should do as much work as it would anyway.
-  settings.image_decode_tasks_enabled = true;
-
   settings.gpu_memory_policy.bytes_limit_when_visible = 512 * 1024 * 1024;
   settings.gpu_memory_policy.priority_cutoff_when_visible =
       gpu::MemoryAllocation::CUTOFF_ALLOW_NICE_TO_HAVE;