Add some public_deps for //headless:headless_lib.

headless/public/util/managed_dispatch_url_request_job.h includes files from //base and //net, so they should be public dependencies.

Example error:
In file included from ../../headless/public/util/deterministic_dispatcher_test.cc:15:
In file included from ../../headless/public/util/testing/fake_managed_dispatch_url_request_job.h:13:
In file included from ../../headless/public/util/managed_dispatch_url_request_job.h:11:
In file included from ../../net/url_request/url_request.h:26:
In file included from ../../net/base/net_error_details.h:9:
In file included from ../../net/http/http_response_info.h:14:
In file included from ../../net/ssl/ssl_info.h:20:
In file included from ../../net/ssl/ssl_config.h:12:
In file included from ../../net/cert/x509_certificate.h:25:
../../third_party/boringssl/src/include/openssl/base.h:68:10: fatal error: 'openssl/opensslconf.h' file not found

BUG=none

Review-Url: https://codereview.chromium.org/2816913002
Cr-Commit-Position: refs/heads/master@{#464473}
diff --git a/headless/BUILD.gn b/headless/BUILD.gn
index 67dcbb4..55afe1f 100644
--- a/headless/BUILD.gn
+++ b/headless/BUILD.gn
@@ -316,11 +316,15 @@
     ]
   }
 
+  public_deps = [
+    "//base",
+    "//net",
+  ]
+
   deps = [
     ":gen_devtools_client_api",
     ":tab_socket",
     ":version_header",
-    "//base",
     "//components/crash/content/browser",
     "//components/security_state/content",
     "//components/security_state/core",
@@ -329,7 +333,6 @@
     "//content/public/child:child",
     "//content/public/common",
     "//content/public/common:service_names",
-    "//net",
     "//services/service_manager/public/cpp",
     "//third_party/mesa:osmesa",
     "//ui/base",