Reland Simplify CanvasAsyncBlobCreator by removing ContextObserver and tests

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

Index: third_party/WebKit/LayoutTests/virtual/threaded/fast/canvas-toBlob/canvas-toBlob-invalid.html
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html b/third_party/WebKit/LayoutTests/virtual/threaded/fast/canvas-toBlob/canvas-toBlob-invalid.html
similarity index 50%
rename from third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html
rename to third_party/WebKit/LayoutTests/virtual/threaded/fast/canvas-toBlob/canvas-toBlob-invalid.html
index c4633f273419f458f2126c1a95c83018b7f7c9c7..679441271fbf7e52ae0f066a55f81869fe0d4e88 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/fast/canvas-toBlob/canvas-toBlob-invalid.html
@@ -1,7 +1,21 @@
-<script src="../../resources/js-test.js"></script>
+<script src="../../../../resources/js-test.js"></script>
 <script type='text/javascript'>
 description("Test the handling of invalid arguments in canvas toBlob().");
 
+if (window.testRunner) {
+    testRunner.dumpAsText();
+    testRunner.waitUntilDone();
+}
+
+var numAsyncCalls = 2;
+function finishOneAsyncCall()
+{
+    numAsyncCalls--;
+    if (numAsyncCalls == 0 && window.testRunner) {
+        testRunner.notifyDone();
+    }
+}
+
 var canvas = document.createElement('canvas');
 var ctx = canvas.getContext("2d"); 
 ctx.strokeStyle = "red";
@@ -11,8 +25,8 @@ shouldThrow("canvas.toBlob();");
 shouldThrow("canvas.toBlob(null);");
 shouldThrow("canvas.toBlob(undefined);");
 // Passing the callback argument without blob handle silently fails.
-shouldNotThrow("canvas.toBlob(function() {});");
+shouldNotThrow("canvas.toBlob(function() { finishOneAsyncCall(); });");
 
 // Invalid quality argument will fall back to default value
-shouldNotThrow("canvas.toBlob(function(blob) {}, 'image/jpeg', 500)");
+shouldNotThrow("canvas.toBlob(function(blob) { finishOneAsyncCall(); }, 'image/jpeg', 500)");
 </script>