Implement a paint offset cache for slimming paint v2

Source/platform/graphics/paint/DrawingRecorder.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 "platform/graphics/paint/DrawingRecorder.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
@@ skipping 31 matching lines @@
 #endif
 {
     if (!RuntimeEnabledFeatures::slimmingPaintEnabled())
         return;
 
     ASSERT(context.displayItemList());
     if (context.displayItemList()->displayItemConstructionIsDisabled())
         return;
 
     // Must check DrawingRecorder::useCachedDrawingIfPossible before creating the DrawingRecorder.
-    ASSERT(!useCachedDrawingIfPossible(m_context, m_displayItemClient, m_displayItemType));
+    ASSERT((RuntimeEnabledFeatures::slimmingPaintV2Enabled() && context.displayItemList()->paintOffsetWasInvalidated(displayItemClient.displayItemClient()))
+        || !useCachedDrawingIfPossible(m_context, m_displayItemClient, m_displayItemType));
 
     ASSERT(DisplayItem::isDrawingType(displayItemType));
 
 #if ENABLE(ASSERT)
     context.setInDrawingRecorder(true);
 #endif
 
     context.beginRecording(cullRect);
 
 #if ENABLE(ASSERT)
@@ skipping 33 matching lines @@
     m_context.displayItemList()->createAndAppend<DrawingDisplayItem>(m_displayItemClient
         , m_displayItemType
         , m_context.endRecording()
 #if ENABLE(ASSERT)
         , m_underInvalidationCheckingMode
 #endif
         );
 }
 
 } // namespace blink