From b7e05b4a9d5cc65cf5a68f9fab111d42932cd711 Mon Sep 17 00:00:00 2001
From: Daosheng Mu <daoshengmu@gmail.com>
Date: Thu, 28 Apr 2016 07:03:45 +0800
Subject: [PATCH 1/2] Avoid drawing while canvases without contexts.

---
 components/layout/display_list_builder.rs | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
index fb2847e9d77..de76e2b20cc 100644
--- a/components/layout/display_list_builder.rs
+++ b/components/layout/display_list_builder.rs
@@ -13,7 +13,7 @@
 use app_units::{Au, AU_PER_PX};
 use azure::azure_hl::Color;
 use block::{BlockFlow, BlockStackingContextType};
-use canvas_traits::{CanvasMsg, CanvasPixelData, CanvasData, FromLayoutMsg};
+use canvas_traits::{CanvasMsg, CanvasData, FromLayoutMsg};
 use context::LayoutContext;
 use euclid::num::Zero;
 use euclid::{Matrix4D, Point2D, Point3D, Rect, SideOffsets2D, Size2D};
@@ -34,7 +34,7 @@ use gfx::paint_thread::THREAD_TINT_COLORS;
 use gfx::text::glyph::CharIndex;
 use gfx_traits::{color, ScrollPolicy};
 use inline::{FIRST_FRAGMENT_OF_ELEMENT, InlineFlow, LAST_FRAGMENT_OF_ELEMENT};
-use ipc_channel::ipc::{self, IpcSharedMemory};
+use ipc_channel::ipc::{self};
 use list_item::ListItemFlow;
 use model::{self, MaybeAuto, ToGfxMatrix};
 use net_traits::image::base::PixelFormat;
@@ -1259,13 +1259,7 @@ impl FragmentDisplayListBuilding for Fragment {
                                 FromLayoutMsg::SendData(sender))).unwrap();
                             receiver.recv().unwrap()
                         },
-                        None => CanvasData::Pixels(CanvasPixelData {
-                            image_data: IpcSharedMemory::from_byte(0xFFu8,
-                                                                   (computed_width *
-                                                                    computed_height * 4)
-                                                                   as usize),
-                            image_key: None,
-                        }),
+                        None => return,
                     };
 
                     let base = state.create_base_display_item(

From f97e6ab9caa702a550a75aadecfd44a6d3de7622 Mon Sep 17 00:00:00 2001
From: Daosheng Mu <daoshengmu@gmail.com>
Date: Thu, 28 Apr 2016 07:04:34 +0800
Subject: [PATCH 2/2] Add test for canvases without contexts.

---
 tests/wpt/mozilla/meta/MANIFEST.json          | 24 +++++++++++++++++++
 .../tests/css/canvas_without_context_a.html   | 15 ++++++++++++
 .../tests/css/canvas_without_context_ref.html | 14 +++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 tests/wpt/mozilla/tests/css/canvas_without_context_a.html
 create mode 100644 tests/wpt/mozilla/tests/css/canvas_without_context_ref.html

diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 4285757014f..b57efe99a79 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -1212,6 +1212,18 @@
             "url": "/_mozilla/css/canvas_radial_gradient_a.html"
           }
         ],
+        "css/canvas_without_context_a.html": [
+          {
+            "path": "css/canvas_without_context_a.html",
+            "references": [
+              [
+                "/_mozilla/css/canvas_without_context_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/canvas_without_context_a.html"
+          }
+        ],
         "css/case-insensitive-font-family.html": [
           {
             "path": "css/case-insensitive-font-family.html",
@@ -7940,6 +7952,18 @@
           "url": "/_mozilla/css/canvas_radial_gradient_a.html"
         }
       ],
+      "css/canvas_without_context_a.html": [
+        {
+          "path": "css/canvas_without_context_a.html",
+          "references": [
+            [
+              "/_mozilla/css/canvas_without_context_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/canvas_without_context_a.html"
+        }
+      ],
       "css/case-insensitive-font-family.html": [
         {
           "path": "css/case-insensitive-font-family.html",
diff --git a/tests/wpt/mozilla/tests/css/canvas_without_context_a.html b/tests/wpt/mozilla/tests/css/canvas_without_context_a.html
new file mode 100644
index 00000000000..b7398f8d59c
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/canvas_without_context_a.html
@@ -0,0 +1,15 @@
+<!doctype html>
+<meta charset="utf-8">
+<link rel="match" href="canvas_without_context_ref.html">
+<style>
+  div {
+    background-color: green;
+    width: 20px;
+    height: 20px;
+  }
+</style>
+</head>
+<body>
+<div><canvas width="20" height="20"></canvas></div>
+</body>
+</html>
diff --git a/tests/wpt/mozilla/tests/css/canvas_without_context_ref.html b/tests/wpt/mozilla/tests/css/canvas_without_context_ref.html
new file mode 100644
index 00000000000..ae0c9c8c8e0
--- /dev/null
+++ b/tests/wpt/mozilla/tests/css/canvas_without_context_ref.html
@@ -0,0 +1,14 @@
+<html>
+<head>
+<style>
+  div {
+    background-color: green;
+    width: 20px;
+    height: 20px;
+  }
+</style>
+</head>
+<body>
+<div></div>
+</body>
+</html>