Refactor RegisterViewportLayers to use a struct instead of 6 values

cc/trees/layer_tree_host_unittest_picture.cc

 // Copyright 2013 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/trees/layer_tree_host.h"
 
 #include "cc/test/fake_content_layer_client.h"
 #include "cc/test/fake_picture_layer.h"
 #include "cc/test/fake_picture_layer_impl.h"
 #include "cc/test/layer_tree_test.h"
@@ skipping 405 matching lines @@
     pinch_->SetIsContainerForFixedPositionLayers(true);
     page_scale_layer->AddChild(pinch_);
     root_clip->AddChild(page_scale_layer);
 
     // Don't be solid color so the layer has tilings/tiles.
     client_.set_fill_with_nonsolid_color(true);
     picture_ = FakePictureLayer::Create(&client_);
     picture_->SetBounds(gfx::Size(100, 100));
     pinch_->AddChild(picture_);
 
-    layer_tree_host()->RegisterViewportLayers(NULL, page_scale_layer, root_clip,
-                                              nullptr, pinch_, nullptr);
+    LayerTreeHost::ViewportLayers viewport_layers;
+    viewport_layers.page_scale = page_scale_layer;
+    viewport_layers.inner_viewport_container = root_clip;
+    viewport_layers.inner_viewport_scroll = pinch_;
+    layer_tree_host()->RegisterViewportLayers(viewport_layers);
     layer_tree_host()->SetPageScaleFactorAndLimits(1.f, 1.f, 4.f);
     layer_tree_host()->SetRootLayer(root_clip);
     LayerTreeHostPictureTest::SetupTree();
     client_.set_bounds(picture_->bounds());
   }
 
   void InitializeSettings(LayerTreeSettings* settings) override {
     settings->layer_transforms_should_scale_layer_contents = true;
   }
 
@@ skipping 238 matching lines @@
   void AfterTest() override {}
 
   scoped_refptr<FakePictureLayer> will_change_layer_;
   scoped_refptr<FakePictureLayer> normal_layer_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostPictureTestForceRecalculateScales);
 
 }  // namespace
 }  // namespace cc