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

third_party/WebKit/Source/core/paint/PaintLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 56 matching lines @@
 class CompositedLayerMapping;
 class CompositorFilterOperations;
 class ComputedStyle;
 class FilterEffect;
 class FilterOperations;
 class HitTestResult;
 class HitTestingTransformState;
 class PaintLayerCompositor;
 class TransformationMatrix;
 
+using PaintLayerId = uint64_t;
+
 enum IncludeSelfOrNot { kIncludeSelf, kExcludeSelf };
 
 enum CompositingQueryMode {
   kCompositingQueriesAreAllowed,
   kCompositingQueriesAreOnlyAllowedInCertainDocumentLifecyclePhases
 };
 
 // FIXME: remove this once the compositing query DCHECKS are no longer hit.
 class CORE_EXPORT DisableCompositingQueryAsserts {
   STACK_ALLOCATED();
@@ skipping 929 matching lines @@
   }
   void ClearSelfPaintingStatusChanged() {
     DCHECK(!RuntimeEnabledFeatures::slimmingPaintV2Enabled());
     self_painting_status_changed_ = false;
   }
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
   void EndShouldKeepAliveAllClientsRecursive();
 #endif
 
+  // An id for this PaintLayer that is unique for the lifetime of the WebView.
+  PaintLayerId UniqueId() const { return unique_id_; }
+
  private:
   void SetNeedsCompositingInputsUpdateInternal();
 
   void Update3DTransformedDescendantStatus();
 
   // Bounding box in the coordinates of this layer.
   LayoutRect LogicalBoundingBox() const;
 
   bool HasOverflowControls() const;
 
@@ skipping 227 matching lines @@
   mutable std::unique_ptr<ClipRectsCache> clip_rects_cache_;
 
   std::unique_ptr<PaintLayerStackingNode> stacking_node_;
 
   IntSize previous_scroll_offset_accumulation_for_painting_;
   RefPtr<ClipRects> previous_clip_rects_;
   LayoutRect previous_paint_dirty_rect_;
 
   std::unique_ptr<PaintLayerRareData> rare_data_;
 
+  PaintLayerId unique_id_;
+
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            DescendantDependentFlagsStopsAtThrottledFrames);
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            PaintLayerTransformUpdatedOnStyleTransformAnimation);
 };
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLayerTree(const blink::PaintLayer*);
 CORE_EXPORT void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif  // Layer_h