Reland Simplify CanvasAsyncBlobCreator by removing ContextObserver and tests

third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html

Index: third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html b/third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html
deleted file mode 100644
index c4633f273419f458f2126c1a95c83018b7f7c9c7..0000000000000000000000000000000000000000
--- a/third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html
+++ /dev/null
@@ -1,18 +0,0 @@
-<script src="../../resources/js-test.js"></script>
-<script type='text/javascript'>
-description("Test the handling of invalid arguments in canvas toBlob().");
-
-var canvas = document.createElement('canvas');
-var ctx = canvas.getContext("2d"); 
-ctx.strokeStyle = "red";
-ctx.strokeRect(0, 0, 50, 50);
-
-shouldThrow("canvas.toBlob();");
-shouldThrow("canvas.toBlob(null);");
-shouldThrow("canvas.toBlob(undefined);");
-// Passing the callback argument without blob handle silently fails.
-shouldNotThrow("canvas.toBlob(function() {});");
-
-// Invalid quality argument will fall back to default value
-shouldNotThrow("canvas.toBlob(function(blob) {}, 'image/jpeg', 500)");
-</script>