[Invalidation Tracking] Add trace events for compositor based invalidations

Source/core/rendering/compositing/CompositingLayerAssigner.cpp

Index: Source/core/rendering/compositing/CompositingLayerAssigner.cpp
diff --git a/Source/core/rendering/compositing/CompositingLayerAssigner.cpp b/Source/core/rendering/compositing/CompositingLayerAssigner.cpp
index f835c9a7e2d28857ee6f3fbd3c56e5c29499c47e..373a95089479f819c5c3a501dcb9e84c10d02c6c 100644
--- a/Source/core/rendering/compositing/CompositingLayerAssigner.cpp
+++ b/Source/core/rendering/compositing/CompositingLayerAssigner.cpp
@@ -27,6 +27,7 @@
 #include "config.h"
 #include "core/rendering/compositing/CompositingLayerAssigner.h"
 
+#include "core/inspector/InspectorTraceEvents.h"
 #include "core/rendering/compositing/CompositedLayerMapping.h"
 #include "platform/TraceEvent.h"
 
@@ -195,6 +196,7 @@ void CompositingLayerAssigner::updateSquashingAssignment(RenderLayer* layer, Squ
         layer->clipper().clearClipRectsIncludingDescendants();
 
         // Issue a paint invalidation, since |layer| may have been added to an already-existing squashing layer.
+        TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::AddedToSquashingLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
     } else if (compositedLayerUpdate == RemoveFromSquashingLayer) {
@@ -206,6 +208,7 @@ void CompositingLayerAssigner::updateSquashingAssignment(RenderLayer* layer, Squ
         }
 
         // If we need to issue paint invalidations, do so now that we've removed it from a squashed layer.
+        TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::RemovedFromSquashingLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
 
@@ -217,6 +220,7 @@ void CompositingLayerAssigner::assignLayersToBackingsForReflectionLayer(RenderLa
 {
     CompositingStateTransitionType compositedLayerUpdate = computeCompositedLayerUpdate(reflectionLayer);
     if (compositedLayerUpdate != NoCompositingStateChange) {
+        TRACE_LAYER_INVALIDATION(reflectionLayer, InspectorLayerInvalidationTrackingEvent::ReflectionLayerChanged);
         layersNeedingPaintInvalidation.append(reflectionLayer);
         m_layersChanged = true;
         m_compositor->allocateOrClearCompositedLayerMapping(reflectionLayer, compositedLayerUpdate);
@@ -239,6 +243,7 @@ void CompositingLayerAssigner::assignLayersToBackingsInternal(RenderLayer* layer
     CompositingStateTransitionType compositedLayerUpdate = computeCompositedLayerUpdate(layer);
 
     if (m_compositor->allocateOrClearCompositedLayerMapping(layer, compositedLayerUpdate)) {
+        TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::NewCompositedLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
     }