Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 6248097b19031e13208183b785a026fa7d0538de..ba435fa1a255686307fda3757ca4de6ee8b01ebe 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2282,6 +2282,8 @@ static void paintScrollbar(const Scrollbar* scrollbar, GraphicsContext& context,
     scrollbar->paint(context, CullRect(transformedClip));
 }
 
+// TODO(eseckler): Make recording distance configurable, e.g. for use in
+// headless, where we would like to record an exact area (distance = 0).
 static const int kPixelDistanceToRecord = 4000;
 
 IntRect CompositedLayerMapping::recomputeInterestRect(const GraphicsLayer* graphicsLayer) const
@@ -2317,7 +2319,7 @@ IntRect CompositedLayerMapping::recomputeInterestRect(const GraphicsLayer* graph
     while (rootView->frame()->ownerLayoutObject())
         rootView = rootView->frame()->ownerLayoutObject()->view();
     anchorLayoutObject->mapToVisualRectInAncestorSpace(rootView, visibleContentRect);
-    visibleContentRect.intersect(LayoutRect(rootView->frameView()->visibleContentRect()));
+    visibleContentRect.intersect(LayoutRect(rootView->frameView()->visibleContentRectForPainting()));
 
     IntRect enclosingGraphicsLayerBounds(enclosingIntRect(graphicsLayerBounds));