Upgrade WebRender

[pcwalton]

This is against an old Servo because I can't build current Servo due to compile errors in RNG crates. I verified that it starts up.

---

• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #23516
• There are tests for these changes

---

This change is 

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/screen.rs, components/script/dom/window.rs
• @KiChjang: components/script/dom/screen.rs, components/net/image_cache.rs, components/script/dom/window.rs, components/script_traits/lib.rs, components/script_traits/script_msg.rs
• @paulrouget: components/compositing/compositor_thread.rs, ports/servo/glutin_app/window.rs, components/servo/lib.rs, components/compositing/compositor.rs, components/compositing/windowing.rs
• @emilio: components/layout/display_list/items.rs, components/layout/display_list/conversions.rs, components/layout/display_list/border.rs, components/layout/display_list/webrender_helpers.rs, components/layout/sequential.rs and 4 more

[highfive]

Warning

• These commits modify net, layout, and script code, but no tests are modified. Please consider adding a test!

[jdm]

@pcwalton The RNG crate problems can usually be resolved by upgrading the crates in question.

[pcwalton]

OK, this one should work.

[jdm]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit c8bcbd1 with merge 9f34412...

[bors-servo]

💔 Test failed - linux-rel-wpt

[bors-servo]

☔ The latest upstream changes (presumably #23468) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit 9913fd9 with merge 65873e6...

[jdm]

This should have addressed all of the previous test failures. Thank you for doing all of the preliminary work, @pcwalton!

[bors-servo]

💔 Test failed - linux-rel-wpt

[Eijebong]

error: unused variable: `clip`
    --> components/layout/display_list/builder.rs:1446:9
     |
1446 |         clip: Rect<Au>,
     |         ^^^^ help: consider prefixing with an underscore: `_clip`
     |
     = note: `-D unused-variables` implied by `-D warnings`

error: aborting due to previous error

Also this needs to be rebased after the diverse rand update thingy (it should dedupe ws and sha1 too)

[jdm]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit bf3878d with merge e558e96...

[bors-servo]

⌛ Testing commit a839835 with merge 8b2e09e...

[bors-servo]

💔 Test failed - status-taskcluster

[CYBAI]

This one pass again in the second Mac build 👀 other failures in other mac builds are #23290

{
  "status": "PASS",
  "group": "default",
  "message": null,
  "stack": null,
  "subtest": null,
  "test": "/css/compositing/mix-blend-mode/mix-blend-mode-both-parent-and-blended-with-3D-transform.html",
  "line": 2057,
  "action": "test_result",
  "expected": "FAIL"
}

besides, in magicleap build:

error[E0432]: unresolved import `servo::webrender_api::DevicePixel`
  --> ports/libmlservo/src/lib.rs:17:5
   |
17 | use servo::webrender_api::DevicePixel;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `DevicePixel` in `webrender_api`

error[E0432]: unresolved import `servo::webrender_api::DevicePoint`
  --> ports/libmlservo/src/lib.rs:18:5
   |
18 | use servo::webrender_api::DevicePoint;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `DevicePoint` in `webrender_api`

error[E0432]: unresolved import `servo::webrender_api::LayoutPixel`
  --> ports/libmlservo/src/lib.rs:19:5
   |
19 | use servo::webrender_api::LayoutPixel;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `LayoutPixel` in `webrender_api`

error: aborting due to 3 previous errors

[jdm]

@bors-servo r=pcwalton,jdm

[bors-servo]

📌 Commit 30ea282 has been approved by pcwalton,jdm

[bors-servo]

⌛ Testing commit 30ea282 with merge df73c71...

[bors-servo]

☀️ Test successful - linux-rel-css, linux-rel-wpt, status-taskcluster
Approved by: pcwalton,jdm
Pushing df73c71 to master...