Bump webdev to 1e47b492c0d364020615128573d12fec928aac07

Changes:
```
> git log --format="%C(auto) %h %s" 5771ee5..1e47b49
 https://dart.googlesource.com/webdev.git/+/1e47b492 [ DWDS ] Write to WebkitDebugger.onClose if the debugger connection closes and the attempts to reconnect fail (2785)
 https://dart.googlesource.com/webdev.git/+/fde4cdfb Prepare test_common/ and fixtures/ for migration (2797)
 https://dart.googlesource.com/webdev.git/+/733ffa67 [webdev] Add a flag used to preview the new DDC module bundle format (2794)
 https://dart.googlesource.com/webdev.git/+/17429c17 Split DDC integration tests between AMD and DDC Library Bundle module systems (2788)
 https://dart.googlesource.com/webdev.git/+/36fc4d73 Add and use TestSdkConfigurationProvider.verbose (2796)
 https://dart.googlesource.com/webdev.git/+/7062b56d Split more DDC tests between AMD and DDC Library Bundle module systems (2789)
 https://dart.googlesource.com/webdev.git/+/7c2e845d Fixing analysis errors in `test/integration`

```

Diff: https://dart.googlesource.com/webdev.git/+/5771ee58119af9835a3005a86fae4556c69d97f0..1e47b492c0d364020615128573d12fec928aac07/
Change-Id: I9c950fdc3cc66381dc6763951b95c7fd185b17e3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/488623
Commit-Queue: Nate Bosch <nbosch@google.com>
Reviewed-by: Kevin Moore <kevmoo@google.com>

DEPS

@@ -153,7 +153,7 @@ vars = {
   "tools_rev": "8f62a7792e30b4b512caa05fb84ce45a57f8d401", # rolled manually to expedite analytics work
   "vector_math_rev": "70fe91cd469c4829b4ec06571a474de79b38a064",
   "web_rev": "48b75126e511e2d3de65130f2e7aa21cca58f473",
-  "webdev_rev": "5771ee58119af9835a3005a86fae4556c69d97f0",
+  "webdev_rev": "1e47b492c0d364020615128573d12fec928aac07",
   "webdriver_rev": "bc92e4e9612a247c4388a7b437ad4e40a5fba1fd",
   "webkit_inspection_protocol_rev": "bb493f55cafb4118f29ebd7cdb995efeafa7f30c",