Track reasons for |Node::SetNeedsStyleRecalc|

Source/core/dom/StyleChangeReason.h

Index: Source/core/dom/StyleChangeReason.h
diff --git a/Source/core/dom/StyleChangeReason.h b/Source/core/dom/StyleChangeReason.h
new file mode 100644
index 0000000000000000000000000000000000000000..b77750d2c7ea9874ca215cde308f9fdf65aa9131
--- /dev/null
+++ b/Source/core/dom/StyleChangeReason.h
@@ -0,0 +1,119 @@
+// 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 StyleChangeReason_h
+#define StyleChangeReason_h
+
+#include "wtf/NullPtr.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class QualifiedName;
+namespace TraceEvent {
+class ConvertableToTraceFormat;
+}
+
+namespace StyleChangeReason {
+extern const char ActiveStylesheetsUpdate[];
+extern const char Animation[];
+extern const char Attribute[];
+extern const char ControlValue[];
+extern const char Control[];
+extern const char DesignMode[];
+extern const char Drag[];
+extern const char FontSizeChange[];
+extern const char Fonts[];
+extern const char FullScreen[];
+extern const char Inline[];
+extern const char Inspector[];
+extern const char Language[];
+extern const char LinkColorChange[];
+extern const char PlatformColorChange[];
+extern const char Plugin[];
+extern const char PropagateInheritChangeToDistributedNodes[];
+extern const char PseudoClass[];
+extern const char SVGContainerSizeChange[];
+extern const char SVGCursor[];
+extern const char SVGFilterLayerUpdate[];
+extern const char Shadow[];
+extern const char SiblingSelector[];
+extern const char StyleInvalidator[];
+extern const char StyleSheetChange[];
+extern const char Validate[];
+extern const char ViewportUnits[];
+extern const char VisitedLink[];
+extern const char VisuallyOrdered[];
+extern const char WritingModeChange[];
+extern const char Zoom[];
+}
+typedef const char StyleChangeReasonString[];
+
+namespace StyleChangeExtraData {
+extern const char Active[];
+extern const char Checked[];
+extern const char Disabled[];
+extern const char Focus[];
+extern const char Hover[];
+extern const char Indeterminate[];
+extern const char Invalid[];
+extern const char LinkVisitedEnabled[];
+extern const char Target[];
+extern const char Unresolved[];
+}
+typedef const char StyleChangeExtraDataString[];
+
+// |StyleChangeReasonForTracing| is used to trace the reason a
+// |Node::setNeedsStyleRecalc| call was made to show it in DevTools or in
+// about:tracing.
+// |StyleChangeReasonForTracing| is strictly only for the tracing purpose as
+// described above. Blink logic must not depend on this value.
+class StyleChangeReasonForTracing {
+public:
+    static StyleChangeReasonForTracing create(StyleChangeReasonString reasonString)
+    {
+        StyleChangeReasonForTracing reason;
+        reason.m_reason = reasonString;
+        reason.m_extraData = nullptr;
+        reason.m_attributeName = nullptr;
+        return reason;
+    }
+
+    static StyleChangeReasonForTracing createWithExtraData(StyleChangeReasonString reasonString, StyleChangeExtraDataString extraData)
+    {
+        StyleChangeReasonForTracing reason;
+        reason.m_reason = reasonString;
+        reason.m_extraData = extraData;
+        reason.m_attributeName = nullptr;
+        return reason;
+    }
+
+    static StyleChangeReasonForTracing fromAttribute(const QualifiedName& attributeName)

[esprehn, 2014/09/26 03:53:01]

qualified name is just namespace and a string, I'd store just the name
(developers don't understand namespaces anyway, and very few pages depend on
them). So you don't need m_attributeName and m_extraData, you only need
m_extraData.

[kouhei (in TOK), 2014/09/29 02:05:32]

Done.

+    {
+        StyleChangeReasonForTracing reason;
+        reason.m_reason = StyleChangeReason::Attribute;
+        reason.m_extraData = nullptr;
+        reason.m_attributeName = &attributeName;
+        return reason;
+    }
+
+    String getReasonString() const;
+    String getExtraDataString() const;

[esprehn, 2014/09/26 03:53:01]

no get* on getters.

[kouhei (in TOK), 2014/09/29 02:05:32]

Done.

+
+private:
+    StyleChangeReasonForTracing() { }
+
+    // disable comparisons
+    const void operator==(const StyleChangeReasonForTracing&) { }
+    const void operator!=(const StyleChangeReasonForTracing&) { }
+
+    const char* m_reason;
+    const char* m_extraData;
+    const QualifiedName* m_attributeName;

[esprehn, 2014/09/26 03:53:01]

remove this. Also QualifiedName is not safe to store in raw ptr form like this,
if the element got removed and gc'ed you'd keep alive the attr qualified name
and have a use after free.

[kouhei (in TOK), 2014/09/29 02:05:32]

Done.

+};
+
+} // namespace blink
+
+#endif // StyleChangeReason_h