8 files changed, 27 insertions, 19 deletions

diff --git a/components/gfx/paint_task.rs b/components/gfx/paint_task.rs
index 43ca598c38a..6fd677495ae 100644
--- a/components/gfx/paint_task.rs
+++ b/components/gfx/paint_task.rs
@@ -382,7 +382,7 @@ impl<C> PaintTask<C> where C: PaintListener + Send + 'static {
                     // When there is a new layer, the transforms and origin
                     // are handled by the compositor.
                     (Some(paint_layer.id),
-                     Point2D::zero(),
+                     -stacking_context.overflow.origin,
                      Matrix4::identity(),
                      Matrix4::identity())
                 }
diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index f7dde7598f8..0485d549c4a 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -1148,9 +1148,6 @@ impl FragmentDisplayListBuilding for Fragment {
                                layer: StackingContextLayer,
                                mode: StackingContextCreationMode)
                                -> Arc<StackingContext> {
-        // FIXME(pcwalton): Is this vertical-writing-direction-safe?
-        let margin = self.margin.to_physical(base_flow.writing_mode);
-
         let border_box = match mode {
             StackingContextCreationMode::Normal |
             StackingContextCreationMode::OuterScrollWrapper => {
@@ -1167,7 +1164,12 @@ impl FragmentDisplayListBuilding for Fragment {
         };
         let overflow = match mode {
             StackingContextCreationMode::Normal => {
-                base_flow.overflow.translate(&-Point2D::new(margin.left, Au(0)))
+                // First, compute the offset of our border box (including relative positioning)
+                // from our flow origin, since that is what `BaseFlow::overflow` is relative to.
+                let border_box_offset =
+                    border_box.translate(&-base_flow.stacking_relative_position).origin;
+                // Then, using that, compute our overflow region relative to our border box.
+                base_flow.overflow.translate(&-border_box_offset)
             }
             StackingContextCreationMode::InnerScrollWrapper |
             StackingContextCreationMode::OuterScrollWrapper => {
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index 8bf88afc701..02af5569d84 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -2060,8 +2060,8 @@ impl Fragment {
         // the time. Can't we handle relative positioning by just adjusting `border_box`?
         let relative_position =
             self.relative_position(&LogicalSize::zero(self.style.writing_mode));
-        border_box =
-            border_box.translate_by_size(&relative_position.to_physical(self.style.writing_mode));
+        border_box = border_box.translate_by_size(&relative_position.to_physical(
+                self.style.writing_mode));
         let mut overflow = border_box;
 
         // Box shadows cause us to draw outside our border box.
diff --git a/tests/ref/basic.list b/tests/ref/basic.list
index fb1d1867ab4..750dc6d1622 100644
--- a/tests/ref/basic.list
+++ b/tests/ref/basic.list
@@ -54,7 +54,7 @@ flaky_cpu == append_style_a.html append_style_b.html
 != block_image.html noteq_500x300_white.html
 == block_replaced_content_a.html block_replaced_content_ref.html
 == block_replaced_content_b.html block_replaced_content_ref.html
-== blur_a.html blur_ref.html
+!= blur_a.html blur_ref.html
 != border_black_groove.html border_black_solid.html
 != border_black_ridge.html border_black_groove.html
 != border_black_ridge.html border_black_solid.html
diff --git a/tests/ref/blur_a.html b/tests/ref/blur_a.html
index 937b21445af..8a589b52b80 100644
--- a/tests/ref/blur_a.html
+++ b/tests/ref/blur_a.html
@@ -6,24 +6,35 @@ div {
    width: 200px;
    height: 200px;
    background: green;
+   position: relative;
 }
 
 .ex {
-   position: relative;
-   width: 40px; height: 40px;
-   border-style: solid;
-   border-color: black;
-   top: 50px; left: 50px;
+   position: absolute;
+   width: 80px; height: 80px;
+   background: blue;
+   top: 60px; left: 60px;
    -webkit-filter: blur(30px);
    -moz-filter: blur(30px);
    filter: blur(30px);
 }
 
+.coveritup {
+   position: absolute;
+   background: green;
+   top: 60px;
+   left: 60px;
+   width: 80px;
+   height: 80px;
+   transform: translateX(0px);  /* force stacking context */
+}
+
 </style>
 </head>
 <body>
   <div>
     <div class="ex"></div>
+    <div class="coveritup"></div>
   </div>
 </body>
 </html>
diff --git a/tests/ref/blur_ref.html b/tests/ref/blur_ref.html
index 1f1996f785f..45795a610c0 100644
--- a/tests/ref/blur_ref.html
+++ b/tests/ref/blur_ref.html
@@ -6,6 +6,7 @@ div {
    width: 200px;
    height: 200px;
    background: green;
+   position: relative;
 }
 
 </style>
diff --git a/tests/wpt/metadata-css/css21_dev/html4/margin-collapse-004.htm.ini b/tests/wpt/metadata-css/css21_dev/html4/margin-collapse-004.htm.ini
deleted file mode 100644
index 3f42fbbb4e7..00000000000
--- a/tests/wpt/metadata-css/css21_dev/html4/margin-collapse-004.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[margin-collapse-004.htm]
-  type: reftest
-  expected: FAIL
diff --git a/tests/wpt/metadata-css/css21_dev/html4/min-height-106.htm.ini b/tests/wpt/metadata-css/css21_dev/html4/min-height-106.htm.ini
deleted file mode 100644
index 83bdbfdf497..00000000000
--- a/tests/wpt/metadata-css/css21_dev/html4/min-height-106.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[min-height-106.htm]
-  type: reftest
-  expected: FAIL