[SPv1] Always set a CompositorElementId on main graphics layers; use PaintLayer id.

third_party/WebKit/Source/platform/graphics/CompositorElementId.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 "platform/RuntimeEnabledFeatures.h"
+
 namespace blink {
 
 static CompositorElementId CreateCompositorElementId(
     uint64_t blink_id,
     CompositorElementIdNamespace namespace_id) {
   DCHECK(
       blink_id > 0 &&
       blink_id <
           std::numeric_limits<uint64_t>::max() /
               static_cast<unsigned>(
                   CompositorElementIdNamespace::kMaxRepresentableNamespaceId));
   // Shift to make room for namespace_id enum bits.
   cc::ElementIdType id = blink_id << kCompositorNamespaceBitCount;
   id += static_cast<uint64_t>(namespace_id);
   return CompositorElementId(id);
 }
 
 CompositorElementId PLATFORM_EXPORT
+CompositorElementIdFromPaintLayerId(PaintLayerId id,
+                                    CompositorElementIdNamespace namespace_id) {
+  DCHECK(namespace_id == CompositorElementIdNamespace::kPrimary ||
+         namespace_id == CompositorElementIdNamespace::kScroll);
+  return CreateCompositorElementId(id, namespace_id);
+}
+
+CompositorElementId PLATFORM_EXPORT
 CompositorElementIdFromDOMNodeId(DOMNodeId id,
                                  CompositorElementIdNamespace namespace_id) {
+  DCHECK(namespace_id == CompositorElementIdNamespace::kViewport ||
+         namespace_id == CompositorElementIdNamespace::kLinkHighlight ||
+         namespace_id == CompositorElementIdNamespace::kRootScroll ||
+         namespace_id == CompositorElementIdNamespace::kScrollState ||
+         namespace_id ==
+             CompositorElementIdNamespace::kPrimaryCompositorProxy ||
+         namespace_id == CompositorElementIdNamespace::kScrollCompositorProxy);
   return CreateCompositorElementId(id, namespace_id);
 }
 
 CompositorElementId PLATFORM_EXPORT
 CompositorElementIdFromScrollbarId(ScrollbarId id,
                                    CompositorElementIdNamespace namespace_id) {
+  DCHECK(namespace_id == CompositorElementIdNamespace::kScrollbar);
   return CreateCompositorElementId(id, namespace_id);
 }
 
 CompositorElementIdNamespace NamespaceFromCompositorElementId(
     CompositorElementId element_id) {
   return static_cast<CompositorElementIdNamespace>(
       element_id.id_ %
       static_cast<uint64_t>(
           CompositorElementIdNamespace::kMaxRepresentableNamespaceId));
 }
 
 }  // namespace blink