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

Source/core/paint/ScopeRecorder.cpp

Index: Source/core/paint/ScopeRecorder.cpp
diff --git a/Source/core/paint/ScopeRecorder.cpp b/Source/core/paint/ScopeRecorder.cpp
index 5b96bc7f0bd87c0764990d18e1784bd472e8c419..8b9eef1d5da98e1a1063f5087f46d8a31ec021f9 100644
--- a/Source/core/paint/ScopeRecorder.cpp
+++ b/Source/core/paint/ScopeRecorder.cpp
@@ -12,23 +12,35 @@
 
 namespace blink {
 
-ScopeRecorder::ScopeRecorder(GraphicsContext& context, const LayoutObject& object)
+ScopeRecorder::ScopeRecorder(GraphicsContext& context, const LayoutObject& object, ShouldBegin shouldBegin)
     : m_displayItemList(context.displayItemList())
     , m_object(object)
+    , m_engaged(false)
 {
+    if (shouldBegin == BeginOnConstruction)
+        begin();
+}
+
+ScopeRecorder::~ScopeRecorder()
+{
+    if (!m_engaged)
+        return;
     if (!RuntimeEnabledFeatures::slimmingPaintEnabled())
         return;
 
-    ASSERT(m_displayItemList);
-    m_displayItemList->beginScope(m_object.displayItemClient());
+    m_displayItemList->endScope(m_object.displayItemClient());
 }
 
-ScopeRecorder::~ScopeRecorder()
+void ScopeRecorder::begin()
 {
+    ASSERT(!m_engaged);
+    m_engaged = true;
+
     if (!RuntimeEnabledFeatures::slimmingPaintEnabled())
         return;
 
-    m_displayItemList->endScope(m_object.displayItemClient());
+    ASSERT(m_displayItemList);
+    m_displayItemList->beginScope(m_object.displayItemClient());
 }
 
 } // namespace blink