Implement initial version of navigator.sendBeacon (#38301)

Gated behind the feature flag `dom_navigator_sendbeacon_enabled` as the
`keep-alive` fetch parameter is crucial for real-life use cases such as
analytics requests.

Part of #4577
Part of #38302

Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>

tests/wpt/include.ini

@@ -3,6 +3,8 @@ skip: true
   skip: false
 [_webgl]
   skip: false
+[beacon]
+  skip: false
 [clipboard-apis]
   skip: false
 [console]

tests/wpt/meta/beacon/beacon-basic.https.window.js.ini

@@ -0,0 +1,12 @@
+[beacon-basic.https.window.html]
+  [Payload size restriction should be accumulated: type = string]
+    expected: FAIL
+
+  [Payload size restriction should be accumulated: type = arraybuffer]
+    expected: FAIL
+
+  [Payload size restriction should be accumulated: type = blob]
+    expected: FAIL
+
+  [sendBeacon() with a stream does not work due to the keepalive flag being set]
+    expected: FAIL

tests/wpt/meta/beacon/beacon-cors.https.window.js.ini

@@ -0,0 +1,6 @@
+[beacon-cors.https.window.html]
+  [cross-origin, non-CORS-safelisted: failure case (without redirect)]
+    expected: FAIL
+
+  [cross-origin, non-CORS-safelisted[credentials=false\]]
+    expected: FAIL

tests/wpt/meta/beacon/headers/header-referrer-no-referrer-when-downgrade.https.html.ini

@@ -0,0 +1,4 @@
+[header-referrer-no-referrer-when-downgrade.https.html]
+  expected: TIMEOUT
+  [Test referer header http://web-platform.test:8000/beacon/resources/]
+    expected: TIMEOUT

tests/wpt/meta/beacon/headers/header-referrer-strict-origin-when-cross-origin.https.html.ini

@@ -0,0 +1,4 @@
+[header-referrer-strict-origin-when-cross-origin.https.html]
+  expected: TIMEOUT
+  [Test referer header http://www1.web-platform.test:8000/beacon/resources/]
+    expected: TIMEOUT

tests/wpt/meta/beacon/headers/header-referrer-strict-origin.https.html.ini

@@ -0,0 +1,4 @@
+[header-referrer-strict-origin.https.html]
+  expected: TIMEOUT
+  [Test referer header http://web-platform.test:8000/beacon/resources/]
+    expected: TIMEOUT

tests/wpt/meta/beacon/headers/header-referrer-unsafe-url.https.html.ini

@@ -0,0 +1,4 @@
+[header-referrer-unsafe-url.https.html]
+  expected: TIMEOUT
+  [Test referer header http://web-platform.test:8000/beacon/resources/]
+    expected: TIMEOUT

tests/wpt/meta/content-security-policy/connect-src/connect-src-beacon-allowed.sub.html.ini

@@ -1,3 +0,0 @@
-[connect-src-beacon-allowed.sub.html]
-  [Expecting logs: ["Pass"\]]
-    expected: NOTRUN

tests/wpt/meta/content-security-policy/connect-src/connect-src-beacon-blocked.sub.html.ini

@@ -1,3 +0,0 @@
-[connect-src-beacon-blocked.sub.html]
-  [Expecting logs: ["Pass", "violated-directive=connect-src"\]]
-    expected: NOTRUN

tests/wpt/meta/content-security-policy/connect-src/connect-src-beacon-redirect-to-blocked.sub.html.ini

@@ -1,3 +0,0 @@
-[connect-src-beacon-redirect-to-blocked.sub.html]
-  [Expecting logs: ["violated-directive=connect-src"\]]
-    expected: NOTRUN

tests/wpt/meta/html/dom/usvstring-reflection.https.html.ini

@@ -14,9 +14,6 @@
   [source : unpaired surrogate codepoint should be replaced with U+FFFD]
     expected: FAIL
 
-  [sendBeacon URL: unpaired surrogate codepoint should not make any exceptions.]
-    expected: FAIL
-
   [RegisterProtocolHandler URL: unpaired surrogate codepoint should not make any exceptions.]
     expected: FAIL
 

tests/wpt/meta/mixed-content/gen/top.http-rp/opt-in/beacon.https.html.ini

@@ -1,6 +1,6 @@
 [beacon.https.html]
-  [Mixed-Content: Expects allowed for beacon to same-https origin and keep-scheme redirection from https context.]
+  [Mixed-Content: Expects blocked for beacon to cross-https origin and swap-scheme redirection from https context.]
     expected: FAIL
 
-  [Mixed-Content: Expects allowed for beacon to same-https origin and no-redirect redirection from https context.]
+  [Mixed-Content: Expects blocked for beacon to same-https origin and swap-scheme redirection from https context.]
     expected: FAIL

tests/wpt/meta/mixed-content/gen/top.meta/opt-in/beacon.https.html.ini

@@ -1,3 +0,0 @@
-[beacon.https.html]
-  [Mixed-Content: Expects allowed for beacon to same-https origin and no-redirect redirection from https context.]
-    expected: FAIL

tests/wpt/meta/mixed-content/gen/top.meta/unset/beacon.https.html.ini

@@ -1,6 +0,0 @@
-[beacon.https.html]
-  [Mixed-Content: Expects allowed for beacon to same-https origin and keep-scheme redirection from https context.]
-    expected: FAIL
-
-  [Mixed-Content: Expects allowed for beacon to same-https origin and no-redirect redirection from https context.]
-    expected: FAIL

tests/wpt/meta/resource-timing/initiator-type/misc.html.ini

@@ -1,2 +1,16 @@
 [misc.html]
-  expected: ERROR
+  expected: TIMEOUT
+  [The initiator type for <body background> must be 'body']
+    expected: FAIL
+
+  [The initiator type for <input type='image'> must be 'input']
+    expected: FAIL
+
+  [The initiator type for <object type='image/png'> must be 'object']
+    expected: FAIL
+
+  [The initiator type for for fetch() must be 'fetch']
+    expected: FAIL
+
+  [The initiator type for new EventSource() must be 'other']
+    expected: TIMEOUT