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..a4a1958195159b1183f92138f762a6899ac8eef9 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
@@ -2312,12 +2314,13 @@ IntRect CompositedLayerMapping::recomputeInterestRect(const GraphicsLayer* graph
     graphicsLayerBoundsInObjectSpace.move(offsetFromAnchorLayoutObject);
 
     // Now map the bounds to its visible content rect in screen space, including applying clips along the way.
-    LayoutRect visibleContentRect(graphicsLayerBoundsInObjectSpace);
+    LayoutRect graphicsLayerBoundsInScreenSpace(graphicsLayerBoundsInObjectSpace);

[chrishtr, 2016/08/22 22:00:42]

It's not screen space, it's the space of the root LayoutView. i.e. it doesn't
include scrolling.

[Eric Seckler, 2016/08/23 09:32:19]

Makes sense, updated the comments as well.

     LayoutView* rootView = anchorLayoutObject->view();
     while (rootView->frame()->ownerLayoutObject())
         rootView = rootView->frame()->ownerLayoutObject()->view();
-    anchorLayoutObject->mapToVisualRectInAncestorSpace(rootView, visibleContentRect);
-    visibleContentRect.intersect(LayoutRect(rootView->frameView()->visibleContentRect()));
+    anchorLayoutObject->mapToVisualRectInAncestorSpace(rootView, graphicsLayerBoundsInScreenSpace);
+    FloatRect visibleContentRect(graphicsLayerBoundsInScreenSpace);
+    rootView->frameView()->clipPaintRect(&visibleContentRect);
 
     IntRect enclosingGraphicsLayerBounds(enclosingIntRect(graphicsLayerBounds));
 
@@ -2325,7 +2328,7 @@ IntRect CompositedLayerMapping::recomputeInterestRect(const GraphicsLayer* graph
     IntRect localInterestRect;
     // If the visible content rect is empty, then it makes no sense to map it back since there is nothing to map.
     if (!visibleContentRect.isEmpty()) {
-        localInterestRect = anchorLayoutObject->absoluteToLocalQuad(FloatRect(visibleContentRect), UseTransforms | TraverseDocumentBoundaries).enclosingBoundingBox();
+        localInterestRect = anchorLayoutObject->absoluteToLocalQuad(visibleContentRect, UseTransforms | TraverseDocumentBoundaries).enclosingBoundingBox();
         localInterestRect.move(-offsetFromAnchorLayoutObject);
         // TODO(chrishtr): the code below is a heuristic, instead we should detect and return whether the mapping failed.
         // In some cases, absoluteToLocalQuad can fail to map back to the local space, due to passing through