From 596193f975f9093d0104d095864462b7afaa081b Mon Sep 17 00:00:00 2001
From: Glenn Watson <gw@intuitionlibrary.com>
Date: Tue, 20 Oct 2015 08:32:17 +1000
Subject: [PATCH] Fix iframes flickering on mouse move.

Fixes #7867 (and probably several other iframe bugs).

When collecting layers for children of a pipeline, pass through the current
subpage pipeline recursively. This prevents descendany layers (such as scroll
layers) from being collected and re-created on the subsequent paint.
---
 components/compositing/compositor_layer.rs | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/components/compositing/compositor_layer.rs b/components/compositing/compositor_layer.rs
index 0bcb35bd28d..525135fd208 100644
--- a/components/compositing/compositor_layer.rs
+++ b/components/compositing/compositor_layer.rs
@@ -449,17 +449,22 @@ impl RcCompositorLayer for Rc<Layer<CompositorData>> {
                 compositor: &mut IOCompositor<Window>,
                 pipeline_id: PipelineId,
                 new_layers: &[LayerProperties],
-                pipelines_removed: &mut Vec<PipelineId>)
+                pipelines_removed: &mut Vec<PipelineId>,
+                layer_pipeline_id: Option<PipelineId>)
                 where Window: WindowMethods {
             // Traverse children first so that layers are removed
             // bottom up - allowing each layer being removed to properly
             // clean up any tiles it owns.
             for kid in &*layer.children() {
+                let extra_data = kid.extra_data.borrow();
+                let layer_pipeline_id = extra_data.subpage_info.or(layer_pipeline_id);
+
                 collect_old_layers_for_pipeline(kid,
                                                 compositor,
                                                 pipeline_id,
                                                 new_layers,
-                                                pipelines_removed);
+                                                pipelines_removed,
+                                                layer_pipeline_id);
             }
 
             // Retain child layers that also exist in the new layer list.
@@ -477,7 +482,7 @@ impl RcCompositorLayer for Rc<Layer<CompositorData>> {
                     }
                 }
 
-                if let Some(layer_pipeline_id) = extra_data.subpage_info {
+                if let Some(layer_pipeline_id) = layer_pipeline_id {
                     for layer_properties in new_layers.iter() {
                         // Keep this layer if a reference to it exists.
                         if let Some(ref subpage_layer_info) = layer_properties.subpage_layer_info {
@@ -507,7 +512,8 @@ impl RcCompositorLayer for Rc<Layer<CompositorData>> {
                                         compositor,
                                         pipeline_id,
                                         new_layers,
-                                        pipelines_removed);
+                                        pipelines_removed,
+                                        None);
     }
 }