Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1224 matching lines @@
     // needs to be set in tandem with the page scale delta.
     if (isVisualViewport)
         m_layer->layer()->setScrollClient(0);
     else
         m_layer->layer()->setScrollClient(this);
 }
 
 void GraphicsLayer::didScroll()
 {
     if (m_scrollableArea) {
-        DoublePoint newPosition = m_scrollableArea->minimumScrollPosition() + toDoubleSize(m_layer->layer()->scrollPositionDouble());
+        DoublePoint newPosition = -m_scrollableArea->scrollOrigin() + toDoubleSize(m_layer->layer()->scrollPositionDouble());
 
         // FrameView::setScrollPosition doesn't work for compositor commits (interacts poorly with programmatic scroll animations)
         // so we need to use the ScrollableArea version. The FrameView method should go away soon anyway.
         m_scrollableArea->ScrollableArea::setScrollPosition(newPosition, CompositorScroll);
     }
 }
 
 std::unique_ptr<base::trace_event::ConvertableToTraceFormat> GraphicsLayer::TakeDebugInfo(cc::Layer* layer)
 {
     std::unique_ptr<base::trace_event::TracedValue> tracedValue(m_debugInfo.asTracedValue());
@@ skipping 124 matching lines @@
 {
     if (!layer) {
         fprintf(stderr, "Cannot showGraphicsLayerTree for (nil).\n");
         return;
     }
 
     String output = layer->layerTreeAsText(blink::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif