Revert "Reland #2: Add vp9-alpha + canvas layout test."

This reverts commit 06f1328a872f9634c096bc7abdda4120b166f7f6.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 632855 as the
culprit for flakes in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vMDZmMTMyOGE4NzJmOTYzNGMwOTZiYzdhYmRkYTQxMjBiMTY2ZjdmNgw

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.mac/WebKit%20Mac10.13%20%28retina%29/10322

Sample Failed Step: webkit_layout_tests on ATI GPU on Mac Retina on Mac-10.13.6

Sample Flaky Test: virtual/video-surface-layer/media/alpha-video-playback.html

Original change's description:
> Reland #2: Add vp9-alpha + canvas layout test.
> 
> Same as the last reland but waits for a requestAnimationFrame
> cycle to ensure the video surface layer has been painted.
> 
> --------------[ Original Description Below ]--------------
> 
> Simply moves the win7 expectation to win since they both use the
> same one. Formats the HTML and adds a title too. Adds an
> expectation for Linux which seems to have changed since last
> landing...
> 
> --------------[ Original Description Below ]--------------
> 
> Apparently we don't have any vpx-alpha layout tests, hence macOS has
> had broken support here for some time.
> 
> BUG=919015
> TEST=fails without the macOS alpha fix.
> TBR=dcastagna
> 
> Change-Id: If89cd6088f06a519b0b7eb1da74feb58040e7442
> Reviewed-on: https://chromium-review.googlesource.com/c/1474518
> Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
> Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#632855}

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
BUG=919015

Change-Id: I669a10f541a0803fef9d1723b8f9bb6526020aa7
Reviewed-on: https://chromium-review.googlesource.com/c/1476212
Cr-Commit-Position: refs/heads/master@{#632897}
diff --git a/third_party/blink/web_tests/media/alpha-video-playback-expected.png b/third_party/blink/web_tests/media/alpha-video-playback-expected.png
deleted file mode 100644
index 59cf826..0000000
--- a/third_party/blink/web_tests/media/alpha-video-playback-expected.png
+++ /dev/null
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diff --git a/third_party/blink/web_tests/media/alpha-video-playback.html b/third_party/blink/web_tests/media/alpha-video-playback.html
deleted file mode 100644
index 06ff9e5..0000000
--- a/third_party/blink/web_tests/media/alpha-video-playback.html
+++ /dev/null
@@ -1,38 +0,0 @@
-<!doctype html>
-<title>Verify VP9+Alpha video playback and canvas interact correctly.</title>
-<style>
-  body { background: white; }
-  video, canvas { background: pink; }
-</style>
-<script>
-  if (window.testRunner)
-    testRunner.waitUntilDone();
-
-  function startTest() {
-    var video = document.querySelector('video');
-
-    video.onplaying = function() {
-      if (video.currentTime == 0) {
-        setTimeout(video.onplaying, 150);
-        return;
-      }
-
-      var canvas = document.querySelector('canvas');
-      var ctx = canvas.getContext('2d');
-
-      // This will squish the video a bit, but it doesn't matter for this test.
-      ctx.clearRect(0, 0, canvas.width, canvas.height);
-      ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
-
-      // Wait for request animation frame to ensure the video frame is drawn.
-      if (window.testRunner)
-        window.requestAnimationFrame(_ => { testRunner.notifyDone(); });
-    }
-
-    video.play();
-  }
-</script>
-<body onload="startTest();">
-  <video src="resources/white-square-vp9a.webm" width="320" height="240"></video>
-  <canvas width="320" height="240"></canvas>
-</body>
diff --git a/third_party/blink/web_tests/media/resources/white-square-vp9a.webm b/third_party/blink/web_tests/media/resources/white-square-vp9a.webm
deleted file mode 100644
index e3d85fb..0000000
--- a/third_party/blink/web_tests/media/resources/white-square-vp9a.webm
+++ /dev/null
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diff --git a/third_party/blink/web_tests/platform/linux/media/alpha-video-playback-expected.png b/third_party/blink/web_tests/platform/linux/media/alpha-video-playback-expected.png
deleted file mode 100644
index 59cf826..0000000
--- a/third_party/blink/web_tests/platform/linux/media/alpha-video-playback-expected.png
+++ /dev/null
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diff --git a/third_party/blink/web_tests/platform/win/media/alpha-video-playback-expected.png b/third_party/blink/web_tests/platform/win/media/alpha-video-playback-expected.png
deleted file mode 100644
index 7096b54..0000000
--- a/third_party/blink/web_tests/platform/win/media/alpha-video-playback-expected.png
+++ /dev/null
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