Enable "gn check" for //third_party/blink/renderer/modules/webtransport

This CL has no behavior changes.

Bug: 800764
Change-Id: Ic4dc91974aa32d01c4fb96ab934b8e1b1c3c51f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2400411
Auto-Submit: Kent Tamura <tkent@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805653}

.gn

@@ -254,7 +254,6 @@ no_check_targets = [
   "//third_party/blink/renderer/modules/canvas:*",  # 1 error
   "//third_party/blink/renderer/modules/font_access:*",  # 3 errors
   "//third_party/blink/renderer/modules/peerconnection:*",  # 43 errors
-  "//third_party/blink/renderer/modules/webtransport:*",  # 16 errors
   "//third_party/blink/renderer/modules:*",  # 321 errors
   "//third_party/blink/renderer/platform:*",  # 72 errors
 

third_party/blink/renderer/modules/webtransport/BUILD.gn

@@ -40,10 +40,13 @@ source_set("unit_tests") {
   ]
 
   deps = [
+    "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
+    "//third_party/blink/renderer/controller:blink_bindings_test_sources",
     "//third_party/blink/renderer/modules",
     "//third_party/blink/renderer/platform",
+    "//third_party/blink/renderer/platform:test_support",
     "//third_party/blink/renderer/platform/wtf",
   ]
 }