Make Chrome behavior the expected one.

As per the current step 3 of "Clip sourceRectangle to the dimensions of input" the cropping rectangle should be clipped to the input's dimensions.
Added early tests for the returned dimension of the ImageBitmap.

Currently Chrome passes all tests, Firefox fails 3 of them.

html/canvas/element/manual/imagebitmap/createImageBitmap-bounds.html

@@ -7,7 +7,7 @@
 <div id="results"></div>
 <script>
 const color = 204;
-function testClip( name, sx, sy, sw, sh, expected ) {
+function testClip( name, sx, sy, sw, sh, expectedColors, expectedWidth, expectedHeight ) {
     promise_test(function(t) {
         return new Promise(function(resolve, reject) {
             const image = new Image();
@@ -17,6 +17,10 @@
         }).then(function(image) {
             return createImageBitmap(image, sx, sy, sw, sh);
         }).then(function(imageBitmap) {
+
+            assert_equals(imageBitmap.width, expectedWidth);
+            assert_equals(imageBitmap.height, expectedHeight);
+
             const canvas = document.createElement("canvas");
             canvas.width = 16;
             canvas.height = 16;
@@ -30,34 +34,34 @@
             ctx.fillRect(0, 0, 20, 20);
             ctx.drawImage(imageBitmap, 0, 0);
 
-            for (let [x, y, r, g, b, a] of expected) {
+            for (let [x, y, r, g, b, a] of expectedColors) {
                 _assertPixel(canvas, x,y, r,g,b,a, `${x},${y}`, `${r},${g},${b},${a}`);
             }
         });
     }, name);
 }
 testClip( "simple clip inside",
-    8, 8, 16, 16, [
+    8, 8, 8, 8, [
         [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
         [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
-    ]
+    ], 8, 8
 );
 testClip( "clip outside negative",
     -8, -8, 16, 16, [
-        [ 4,  4, color,color,color,255], [12, 4,  color,color,color,255],
-        [ 4, 12, color,color,color,255], [12, 12, 0,255,0,255]
-    ]
+        [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
+        [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
+    ], 8, 8
 );
 testClip( "clip outside positive",
     8, 8, 16, 16, [
-      [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
-      [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
-    ]
+        [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
+        [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
+    ], 8, 8
 );
 testClip( "clip inside using negative width and height",
-  24, 24, -16, -16, [
-    [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
-    [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
-  ]
+    24, 24, -16, -16, [
+        [ 4,  4, 0,255,0,255],           [12,  4, color,color,color,255],
+        [ 4, 12, color,color,color,255], [12, 12, color,color,color,255]
+    ], 8, 8
 );
 </script>