Allow certain SP recorder classes to defer their "begin" operation.

Source/core/paint/FloatClipRecorder.cpp

 // 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.
 
 #include "config.h"
 #include "core/paint/FloatClipRecorder.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 #include "platform/graphics/paint/FloatClipDisplayItem.h"
 
 namespace blink {
 
-FloatClipRecorder::FloatClipRecorder(GraphicsContext& context, const DisplayItemClientWrapper& client, PaintPhase paintPhase, const FloatRect& clipRect)
+FloatClipRecorder::FloatClipRecorder(GraphicsContext& context, const DisplayItemClientWrapper& client, PaintPhase paintPhase)
     : m_context(context)
     , m_client(client)
     , m_clipType(DisplayItem::paintPhaseToFloatClipType(paintPhase))
 {
-    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
-        ASSERT(m_context.displayItemList());
-        if (m_context.displayItemList()->displayItemConstructionIsDisabled())
-            return;
-        m_context.displayItemList()->add(FloatClipDisplayItem::create(m_client, m_clipType, clipRect));
-    } else {
-        FloatClipDisplayItem clipDisplayItem(m_client, m_clipType, clipRect);
-        clipDisplayItem.replay(m_context);
-    }
+}
+
+FloatClipRecorder::FloatClipRecorder(GraphicsContext& context, const DisplayItemClientWrapper& client, PaintPhase paintPhase, const FloatRect& clipRect)
+    : FloatClipRecorder(context, client, paintPhase)
+{
+    begin(clipRect);
 }
 
 FloatClipRecorder::~FloatClipRecorder()
 {
+    if (!m_engaged)
+        return;
+
     DisplayItem::Type endType = DisplayItem::floatClipTypeToEndFloatClipType(m_clipType);
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         ASSERT(m_context.displayItemList());
         if (m_context.displayItemList()->displayItemConstructionIsDisabled())
             return;
         m_context.displayItemList()->add(EndFloatClipDisplayItem::create(m_client, endType));
     } else {
         EndFloatClipDisplayItem endClipDisplayItem(m_client, endType);
         endClipDisplayItem.replay(m_context);
     }
 }
 
+void FloatClipRecorder::begin(const FloatRect& clipRect)
+{
+    ASSERT(!m_engaged);
+    m_engaged = true;
+
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+        ASSERT(m_context.displayItemList());
+        if (m_context.displayItemList()->displayItemConstructionIsDisabled())
+            return;
+        m_context.displayItemList()->add(FloatClipDisplayItem::create(m_client, m_clipType, clipRect));
+    } else {
+        FloatClipDisplayItem clipDisplayItem(m_client, m_clipType, clipRect);
+        clipDisplayItem.replay(m_context);
+    }
+}
+
 } // namespace blink