Set layer element id when building layers in PaintArtifactCompositor.

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositorTest.cpp

 // Copyright 2016 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 "platform/graphics/compositing/PaintArtifactCompositor.h"
 
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/layers/layer.h"
 #include "cc/test/fake_compositor_frame_sink.h"
@@ skipping 668 matching lines @@
   ASSERT_EQ(3u, scrollTree.size());
   const cc::ScrollNode& scrollNode = *scrollTree.Node(2);
   EXPECT_EQ(gfx::Size(11, 13), scrollNode.scroll_clip_layer_bounds);
   EXPECT_EQ(gfx::Size(27, 31), scrollNode.bounds);
   EXPECT_TRUE(scrollNode.user_scrollable_horizontal);
   EXPECT_FALSE(scrollNode.user_scrollable_vertical);
   EXPECT_EQ(1, scrollNode.parent_id);
   EXPECT_EQ(expectedCompositorElementId, scrollNode.element_id);
   EXPECT_EQ(scrollNode.id,
             elementIdToScrollNodeIndex(expectedCompositorElementId));
+  EXPECT_EQ(expectedCompositorElementId, contentLayerAt(0)->element_id());
 
   const cc::TransformTree& transformTree = propertyTrees().transform_tree;
   const cc::TransformNode& transformNode =
       *transformTree.Node(scrollNode.transform_id);
   EXPECT_TRUE(transformNode.local.IsIdentity());
 
   EXPECT_EQ(gfx::ScrollOffset(-7, -9),
             scrollTree.current_scroll_offset(contentLayerAt(0)->id()));
 
   EXPECT_EQ(MainThreadScrollingReason::kNotScrollingOnMain,
@@ skipping 45 matching lines @@
   EXPECT_EQ(gfx::Size(29, 31), scrollNodeB.bounds);
   EXPECT_TRUE(scrollNodeB.user_scrollable_horizontal);
   EXPECT_FALSE(scrollNodeB.user_scrollable_vertical);
   EXPECT_EQ(scrollNodeA.id, scrollNodeB.parent_id);
   EXPECT_EQ(expectedCompositorElementIdA, scrollNodeA.element_id);
   EXPECT_EQ(scrollNodeA.id,
             elementIdToScrollNodeIndex(expectedCompositorElementIdA));
   EXPECT_EQ(expectedCompositorElementIdB, scrollNodeB.element_id);
   EXPECT_EQ(scrollNodeB.id,
             elementIdToScrollNodeIndex(expectedCompositorElementIdB));
+  EXPECT_EQ(expectedCompositorElementIdA, contentLayerAt(0)->element_id());
+  EXPECT_EQ(expectedCompositorElementIdB, contentLayerAt(1)->element_id());
 
   const cc::TransformTree& transformTree = propertyTrees().transform_tree;
   const cc::TransformNode& transformNodeA =
       *transformTree.Node(scrollNodeA.transform_id);
   EXPECT_TRUE(transformNodeA.local.IsIdentity());
   const cc::TransformNode& transformNodeB =
       *transformTree.Node(scrollNodeB.transform_id);
   EXPECT_TRUE(transformNodeB.local.IsIdentity());
 
   EXPECT_EQ(gfx::ScrollOffset(-11, -13),
@@ skipping 805 matching lines @@
   chunk3.properties.propertyTreeState = chunk1.properties.propertyTreeState;
   chunk3.bounds = FloatRect(0, 0, 50, 60);
   chunk3.knownToBeOpaque = true;
   pendingLayer.add(chunk3, nullptr);
 
   // Chunk 3 covers the entire layer, so now it's opaque.
   EXPECT_TRUE(pendingLayer.knownToBeOpaque);
 }
 
 }  // namespace blink