cc : Move screen space scale factor to root transform node

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index acc34795448ed974e952394e018b5092d051f8e9..dddba3637390bb3f6c6a22b9cc5768d4935666ad 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -607,11 +607,9 @@ void TransformTree::UpdateTargetSpaceTransform(TransformNode* node,
     // to the root of the transform tree in ComputeTransform.
     int target_id = target_node->id;
     ComputeTransform(node->id, target_id, &target_space_transform);
-    if (target_id != kRootNodeId) {
-      target_space_transform.matrix().postScale(
-          target_node->surface_contents_scale.x(),
-          target_node->surface_contents_scale.y(), 1.f);
-    }
+    target_space_transform.matrix().postScale(
+        target_node->surface_contents_scale.x(),
+        target_node->surface_contents_scale.y(), 1.f);
   }
 
   gfx::Transform from_target;
@@ -707,15 +705,18 @@ void TransformTree::UpdateNodeAndAncestorsAreAnimatedOrInvertible(
 
 void TransformTree::SetDeviceTransform(const gfx::Transform& transform,
                                        gfx::PointF root_position) {
-  gfx::Transform root_post_local = transform;
-  TransformNode* node = Node(1);
-  root_post_local.Scale(node->post_local_scale_factor,
-                        node->post_local_scale_factor);
-  root_post_local.Translate(root_position.x(), root_position.y());
-  if (node->post_local == root_post_local)
+  gfx::Vector2dF device_transform_scale_components =
+      MathUtil::ComputeTransform2dScaleComponents(transform, 1.f);
+  gfx::Transform post_local = transform;
+  post_local.matrix().postScale(1.f / device_transform_scale_components.x(),
+                                1.f / device_transform_scale_components.y(),
+                                1.f);
+  post_local.Translate(root_position.x(), root_position.y());
+
+  TransformNode* node = Node(kContentsRootNodeId);
+  if (node->post_local == post_local)
     return;
-
-  node->post_local = root_post_local;
+  node->post_local = post_local;
   node->needs_local_transform_update = true;
   set_needs_update(true);
 }
@@ -731,6 +732,32 @@ void TransformTree::SetDeviceTransformScaleFactor(
                device_transform_scale_components.y());
 }
 
+void TransformTree::SetScreenSpaceScale(float device_scale_factor,
+                                        float page_scale_factor_for_root,
+                                        gfx::Transform device_transform) {
+  gfx::Vector2dF device_transform_scale_components =
+      MathUtil::ComputeTransform2dScaleComponents(device_transform, 1.f);
+  gfx::Vector2dF screen_space_scale_components(
+      device_transform_scale_components.x() * device_scale_factor *
+          page_scale_factor_for_root,
+      device_transform_scale_components.y() * device_scale_factor *
+          page_scale_factor_for_root);
+  TransformNode* node = Node(kRootNodeId);
+  if (node->surface_contents_scale == screen_space_scale_components)
+    return;
+  node->needs_surface_contents_scale = true;
+  node->surface_contents_scale = screen_space_scale_components;
+  gfx::Transform to_screen;
+  to_screen.Scale(node->surface_contents_scale.x(),
+                  node->surface_contents_scale.y());
+  SetToScreen(node->id, to_screen);
+  gfx::Transform from_screen;
+  if (!ToScreen(node->id).GetInverse(&from_screen))
+    node->ancestors_are_invertible = false;
+  SetFromScreen(node->id, from_screen);
+  set_needs_update(true);
+}
+
 void TransformTree::UpdateInnerViewportContainerBoundsDelta() {
   if (nodes_affected_by_inner_viewport_bounds_delta_.empty())
     return;
@@ -1027,8 +1054,7 @@ void EffectTree::UpdateBackfaceVisibility(EffectNode* node,
 }
 
 void EffectTree::UpdateSurfaceContentsScale(EffectNode* effect_node) {
-  if (!effect_node->has_render_surface ||
-      effect_node->transform_id == kRootNodeId) {
+  if (!effect_node->has_render_surface) {
     effect_node->surface_contents_scale = gfx::Vector2dF(1.0f, 1.0f);
     return;
   }
@@ -1148,11 +1174,8 @@ void EffectTree::TakeCopyRequestsAndTransformToSurface(
     gfx::Transform transform;
     property_trees()->transform_tree.ComputeTransform(source_id, destination_id,
                                                       &transform);
-    if (effect_node->id != kContentsRootNodeId) {
-      transform.matrix().postScale(effect_node->surface_contents_scale.x(),
-                                   effect_node->surface_contents_scale.y(),
-                                   1.f);
-    }
+    transform.matrix().postScale(effect_node->surface_contents_scale.x(),
+                                 effect_node->surface_contents_scale.y(), 1.f);
     it->set_area(MathUtil::MapEnclosingClippedRect(transform, it->area()));
   }
 }