Remove image_decode_tasks_enabled flag.

cc/trees/layer_tree_host_unittest_checkerimaging.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/base/completion_event.h"
 #include "cc/test/begin_frame_args_test.h"
 #include "cc/test/fake_content_layer_client.h"
 #include "cc/test/fake_external_begin_frame_source.h"
 #include "cc/test/fake_picture_layer.h"
 #include "cc/test/layer_tree_test.h"
 #include "cc/test/skia_common.h"
 #include "cc/test/test_compositor_frame_sink.h"
 #include "cc/trees/layer_tree_impl.h"
 
 namespace cc {
 namespace {
 
 class LayerTreeHostCheckerImagingTest : public LayerTreeTest {
  public:
   void BeginTest() override { PostSetNeedsCommitToMainThread(); }
   void AfterTest() override {}
 
   void InitializeSettings(LayerTreeSettings* settings) override {
-    settings->image_decode_tasks_enabled = true;
     settings->enable_checker_imaging = true;
   }
 
   void SetupTree() override {
     // Set up a content client which creates the following tiling, x denoting
     // the image to checker:
     // |---|---|---|---|
     // | x | x |   |   |
     // |---|---|---|---|
     // | x | x |   |   |
@@ skipping 152 matching lines @@
 
   int num_of_activations_ = 0;
   int num_of_commits_ = 0;
   int num_of_impl_side_invalidations_ = 0;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostCheckerImagingTestImplSideTree);
 
 }  // namespace
 }  // namespace cc