Add a new top-level inspector timeline event for the PrePaint step

third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h

Index: third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h
diff --git a/third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h b/third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h
index b5e314c762e95692ecf66b22208b03798a3d006a..d71910d3d24e92bb8166ab1aea729296365c306a 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h
+++ b/third_party/WebKit/Source/core/inspector/InspectorTraceEvents.h
@@ -285,6 +285,10 @@ std::unique_ptr<TracedValue> data(const PaintLayer*, const char* reason);
       "LayerInvalidationTracking", TRACE_EVENT_SCOPE_THREAD, "data",       \
       InspectorLayerInvalidationTrackingEvent::data((LAYER), (REASON)));
 
+namespace InspectorPreparePaintEvent {
+std::unique_ptr<TracedValue> data(LocalFrame*);
+}
+
 namespace InspectorPaintEvent {
 std::unique_ptr<TracedValue> data(LayoutObject*,
                                   const LayoutRect& clipRect,