Remove image_decode_tasks_enabled flag.

content/test/fake_compositor_dependencies.cc

Index: content/test/fake_compositor_dependencies.cc
diff --git a/content/test/fake_compositor_dependencies.cc b/content/test/fake_compositor_dependencies.cc
index 28065e9eddb56a9739a64ea44044700e27e10b3b..1cb9e0b3c488b2b9ca10e727f0eb883c02f437d7 100644
--- a/content/test/fake_compositor_dependencies.cc
+++ b/content/test/fake_compositor_dependencies.cc
@@ -80,10 +80,6 @@ cc::TaskGraphRunner* FakeCompositorDependencies::GetTaskGraphRunner() {
   return &task_graph_runner_;
 }
 
-bool FakeCompositorDependencies::AreImageDecodeTasksEnabled() {
-  return false;
-}
-
 bool FakeCompositorDependencies::IsThreadedAnimationEnabled() {
   return true;
 }