Begin tracking why layout is invalidated

Source/core/inspector/InspectorTraceEvents.h

 // Copyright 2014 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.
 
 #ifndef InspectorTraceEvents_h
 #define InspectorTraceEvents_h
 
 #include "core/css/CSSSelector.h"
 #include "platform/EventTracer.h"
 #include "platform/TraceEvent.h"
@@ skipping 90 matching lines @@
         "data", \
         InspectorStyleInvalidatorInvalidateEvent::data((element), (InspectorStyleInvalidatorInvalidateEvent::reason)))
 
 #define TRACE_STYLE_INVALIDATOR_INVALIDATION_SELECTORPART(element, reason, invalidationSet, singleSelectorPart) \
     TRACE_EVENT_INSTANT1( \
         TRACE_DISABLED_BY_DEFAULT("devtools.timeline.invalidationTracking"), \
         "StyleInvalidatorInvalidationTracking", \
         "data", \
         InspectorStyleInvalidatorInvalidateEvent::selectorPart((element), (InspectorStyleInvalidatorInvalidateEvent::reason), (invalidationSet), (singleSelectorPart)))
 
+// From a web developer's perspective: what caused this layout? This is strictly
+// for tracing. Blink logic must not depend on these.
+namespace LayoutInvalidationReason {
+extern const char Unknown[];
+extern const char SizeChanged[];
+extern const char AncestorMoved[];
+extern const char StyleChange[];
+extern const char DomChanged[];
+extern const char TextChanged[];
+extern const char PrintingChanged[];
+extern const char AttributeChanged[];
+extern const char ColumnsChanged[];
+extern const char ChildAnonymousBlockChanged[];
+extern const char AnonymousBlockChange[];
+extern const char Fullscreen[];
+extern const char ChildChanged[];
+extern const char ListValueChange[];
+extern const char ImageChanged[];
+extern const char LineBoxesChanged[];
+extern const char SliderValueChanged[];
+extern const char AncestorMarginCollapsing[];
+extern const char FieldsetChanged[];
+extern const char TextAutosizing[];
+extern const char SvgResourceInvalidated[];
+}
+
+// LayoutInvalidationReasonForTracing is strictly for tracing. Blink logic must
+// not depend on this value.
+typedef const char LayoutInvalidationReasonForTracing[];
+
 class InspectorLayoutInvalidationTrackingEvent {
 public:
-    static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(const LayoutObject*);
+    static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(const LayoutObject*, LayoutInvalidationReasonForTracing);
 };
 
 class InspectorPaintInvalidationTrackingEvent {
 public:
     static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(const LayoutObject* renderer, const LayoutObject* paintContainer);
 };
 
 class InspectorSendRequestEvent {
 public:
     static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(unsigned long identifier, LocalFrame*, const ResourceRequest&);
@@ skipping 170 matching lines @@
 
 class InspectorAnimationStateEvent {
 public:
     static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(const AnimationPlayer&);
 };
 
 } // namespace blink
 
 
 #endif // !defined(InspectorTraceEvents_h)