cc : Move screen space scale factor to root transform node

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp

Index: third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
index a9927e99f8e35ebc9095a118ee46e1ab56bbf9cc..6f318359c6edeafa50537360aad811dcb11cdd17 100644
--- a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
+++ b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp
@@ -454,8 +454,21 @@ class PropertyTreeManager {
 };
 
 void PropertyTreeManager::setDeviceScaleFactor(float deviceScaleFactor) {
-  auto& rootTransformNode = *transformTree().Node(kSecondaryRootNodeId);
-  rootTransformNode.local.Scale(deviceScaleFactor, deviceScaleFactor);
+  auto& rootTransformNode = *transformTree().Node(kRealRootNodeId);
+  rootTransformNode.needs_surface_contents_scale = true;
+  rootTransformNode.surface_contents_scale =
+      gfx::Vector2dF(deviceScaleFactor, deviceScaleFactor);
+  // TODO(jaydasika) : We shouldn't set ToScreen and FromScreen of root

[weiliangc, 2016/10/13 21:16:18]

Why does this not work in cc right now?

[jaydasika, 2016/10/13 21:46:48]

It doesn't work. We only update transforms from node 1. In cc, you can see a
similar update for node 0 in SetScreenSpaceScale. I plan to remove them in a
follow-up.  

+  // transform node here. They should be set while updating transform tree in
+  // cc.
+  gfx::Transform toScreen;
+  toScreen.Scale(deviceScaleFactor, deviceScaleFactor);
+  transformTree().SetToScreen(rootTransformNode.id, toScreen);
+  gfx::Transform fromScreen;
+  if (!toScreen.GetInverse(&fromScreen))
+    rootTransformNode.ancestors_are_invertible = false;
+  transformTree().SetFromScreen(rootTransformNode.id, fromScreen);
+  transformTree().set_needs_update(true);
 }
 
 int PropertyTreeManager::compositorIdForTransformNode(