headless: allow unittests to depend on generated headers

This fixes `gn check` for the headless_unittests target.

Bug: 1158989
Change-Id: I2e65534bc775ae21975d59c714489965e659ab2e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3388271
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#960714}

.gn

@@ -78,8 +78,6 @@ no_check_targets = [
   "//headless:headless_shared_sources",  # 4 errors
   "//headless:headless_shell_browser_lib",  # 10 errors
   "//headless:headless_shell_lib",  # 10 errors
-  "//headless:headless_unittests",  # 6 errors
-  "//headless:headless_unittests__exec",
 
   "//third_party/libwebp:*",  # 7 errors, https://crbug.com/800762
 

headless/BUILD.gn

@@ -171,18 +171,21 @@ devtools_domains = [
   "tracing",
 ]
 
-generated_devtools_api = []
+generated_devtools_api_sources = []
+generated_devtools_api_headers = []
 foreach(domain, devtools_domains) {
-  generated_devtools_api += [
-    "$target_gen_dir/public/devtools/domains/" + domain + ".cc",
+  generated_devtools_api_headers += [
     "$target_gen_dir/public/devtools/domains/" + domain + ".h",
     "$target_gen_dir/public/devtools/domains/types_" + domain + ".h",
-    "$target_gen_dir/public/devtools/domains/types_" + domain + ".cc",
     "$target_gen_dir/public/devtools/internal/type_conversions_" + domain +
         ".h",
     "$target_gen_dir/public/devtools/internal/" +
         "types_forward_declarations_" + domain + ".h",
   ]
+  generated_devtools_api_sources += [
+    "$target_gen_dir/public/devtools/domains/" + domain + ".cc",
+    "$target_gen_dir/public/devtools/domains/types_" + domain + ".cc",
+  ]
 }
 
 action("gen_devtools_client_api") {
@@ -195,7 +198,7 @@ action("gen_devtools_client_api") {
     "$root_gen_dir/third_party/blink/public/devtools_protocol/protocol.json",
   ]
 
-  outputs = generated_devtools_api
+  outputs = generated_devtools_api_headers + generated_devtools_api_sources
   sources = [
     "lib/browser/devtools_api/domain_cc.template",
     "lib/browser/devtools_api/domain_h.template",
@@ -308,7 +311,7 @@ source_set("headless_shared_sources") {
     "public/util/user_agent.h",
   ]
 
-  sources += generated_devtools_api
+  sources += generated_devtools_api_headers + generated_devtools_api_sources
 
   if (!is_fuchsia) {
     sources += [
@@ -690,10 +693,20 @@ test("headless_unittests") {
   sources = [
     "public/domains/types_unittest.cc",
     "public/util/error_reporter_unittest.cc",
+
+    # Headers for code under test that aren't normally exposed.
+    "public/headless_export.h",
+    "public/util/error_reporter.h",
   ]
+
+  # Headers for generated API code under test.
+  sources += generated_devtools_api_headers
+
   defines = []
 
   deps = [
+    ":gen_devtools_client_api",
+    ":headless_non_renderer",
     ":headless_shell_lib",
     "//base/test:run_all_unittests",
     "//base/test:test_support",