First version of new merge algorithm (not enabled yet)

Source/core/paint/SubtreeRecorder.cpp

Index: Source/core/paint/SubtreeRecorder.cpp
diff --git a/Source/core/paint/SubtreeRecorder.cpp b/Source/core/paint/SubtreeRecorder.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..147925e3db06db70bff75923f8f86ef897ed99a1
--- /dev/null
+++ b/Source/core/paint/SubtreeRecorder.cpp
@@ -0,0 +1,56 @@
+// Copyright 2015 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.
+
+#include "config.h"
+#include "core/paint/SubtreeRecorder.h"
+
+#include "core/layout/LayoutObject.h"
+#include "platform/RuntimeEnabledFeatures.h"
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/paint/DisplayItemList.h"
+#include "platform/graphics/paint/SubtreeDisplayItem.h"
+
+namespace blink {
+
+SubtreeRecorder::SubtreeRecorder(GraphicsContext* context, const LayoutObject& subtreeRoot, PaintPhase paintPhase)
+    : m_displayItemList(context->displayItemList())
+    , m_subtreeRoot(subtreeRoot)
+    , m_paintPhase(paintPhase)
+    , m_begun(false)
+{
+    if (!RuntimeEnabledFeatures::slimmingPaintEnabled() || !RuntimeEnabledFeatures::slimmingPaintDisplayItemCacheEnabled())
+        return;
+
+    ASSERT(m_displayItemList);
+}
+
+SubtreeRecorder::~SubtreeRecorder()
+{
+    if (!RuntimeEnabledFeatures::slimmingPaintEnabled() || !RuntimeEnabledFeatures::slimmingPaintDisplayItemCacheEnabled())
+        return;
+
+    if (m_begun)
+        addDisplayItem(EndSubtreeDisplayItem::create(m_subtreeRoot.displayItemClient(), DisplayItem::paintPhaseToEndSubtreeType(m_paintPhase)));
+    else if (m_displayItemList->clientCacheIsValid(m_subtreeRoot.displayItemClient()))
+        addDisplayItem(SubtreeCachedDisplayItem::create(m_subtreeRoot.displayItemClient(), DisplayItem::paintPhaseToSubtreeCachedType(m_paintPhase)));
+}
+
+void SubtreeRecorder::begin()
+{
+    if (!RuntimeEnabledFeatures::slimmingPaintEnabled() || !RuntimeEnabledFeatures::slimmingPaintDisplayItemCacheEnabled())
+        return;
+
+    addDisplayItem(BeginSubtreeDisplayItem::create(m_subtreeRoot.displayItemClient(), DisplayItem::paintPhaseToBeginSubtreeType(m_paintPhase)));
+    m_begun = true;
+}
+
+void SubtreeRecorder::addDisplayItem(PassOwnPtr<DisplayItem> displayItem)
+{
+#ifndef NDEBUG
+    displayItem->setClientDebugString(String::format("subtreeRoot: \"%p %s\"", &m_subtreeRoot, m_subtreeRoot.debugName().utf8().data()));
+#endif
+    m_displayItemList->add(displayItem);
+}
+
+} // namespace blink