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

Source/core/paint/CompositingRecorder.cpp

Index: Source/core/paint/CompositingRecorder.cpp
diff --git a/Source/core/paint/CompositingRecorder.cpp b/Source/core/paint/CompositingRecorder.cpp
index 8d68e46828114ae148889c7e4f7d0ed0663eb0eb..2a2b5c9fe2e26e6df981962a2198e036ca9a5bbf 100644
--- a/Source/core/paint/CompositingRecorder.cpp
+++ b/Source/core/paint/CompositingRecorder.cpp
@@ -13,16 +13,30 @@
 
 namespace blink {
 
-CompositingRecorder::CompositingRecorder(GraphicsContext& graphicsContext, const DisplayItemClientWrapper& client, const SkXfermode::Mode xferMode, const float opacity, const FloatRect* bounds, ColorFilter colorFilter)
+CompositingRecorder::CompositingRecorder(GraphicsContext& graphicsContext, const DisplayItemClientWrapper& client)
     : m_client(client)
     , m_graphicsContext(graphicsContext)
+    , m_engaged(false)
 {
-    beginCompositing(graphicsContext, m_client, xferMode, opacity, bounds, colorFilter);
+}
+
+CompositingRecorder::CompositingRecorder(GraphicsContext& graphicsContext, const DisplayItemClientWrapper& client, SkXfermode::Mode xferMode, float opacity, const FloatRect* bounds, ColorFilter colorFilter)
+    : CompositingRecorder(graphicsContext, client)
+{
+    begin(xferMode, opacity, bounds, colorFilter);
 }
 
 CompositingRecorder::~CompositingRecorder()
 {
-    endCompositing(m_graphicsContext, m_client);
+    if (m_engaged)
+        endCompositing(m_graphicsContext, m_client);
+}
+
+void CompositingRecorder::begin(SkXfermode::Mode xferMode, float opacity, const FloatRect* bounds, ColorFilter colorFilter)
+{
+    ASSERT(!m_engaged);
+    m_engaged = true;
+    beginCompositing(m_graphicsContext, m_client, xferMode, opacity, bounds, colorFilter);
 }
 
 void CompositingRecorder::beginCompositing(GraphicsContext& graphicsContext, const DisplayItemClientWrapper& client, const SkXfermode::Mode xferMode, const float opacity, const FloatRect* bounds, ColorFilter colorFilter)