Stop retrieving scrolling element id from the CompositorElementId.

third_party/WebKit/Source/platform/graphics/CompositorElementIdTest.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/CompositorElementId.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
 
 class CompositorElementIdTest : public ::testing::Test {};
 
+uint64_t IdFromCompositorElementId(CompositorElementId element_id) {
+  return element_id.id_ >> kCompositorNamespaceBitCount;
+}
+
 TEST_F(CompositorElementIdTest, EncodeDecode) {
   CompositorElementId element_id = CompositorElementIdFromDOMNodeId(
       1, CompositorElementIdNamespace::kPrimary);
   EXPECT_EQ(1u, IdFromCompositorElementId(element_id));
   EXPECT_EQ(CompositorElementIdNamespace::kPrimary,
             NamespaceFromCompositorElementId(element_id));
 
   element_id = CompositorElementIdFromDOMNodeId(
       1, CompositorElementIdNamespace::kLinkHighlight);
   EXPECT_EQ(1u, IdFromCompositorElementId(element_id));
   EXPECT_EQ(CompositorElementIdNamespace::kLinkHighlight,
             NamespaceFromCompositorElementId(element_id));
 
   element_id = CompositorElementIdFromDOMNodeId(
       23, CompositorElementIdNamespace::kScroll);
   EXPECT_EQ(23u, IdFromCompositorElementId(element_id));
   EXPECT_EQ(CompositorElementIdNamespace::kScroll,
             NamespaceFromCompositorElementId(element_id));
 }
 
 }  // namespace blink