Move debug_devtools to a buildflag_header.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 2545e809ed6831402a81c9800e3cf0f58d821fb5..ed21b1ca7f06009fc5842ebc9159a1c81f1cb3fd 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -1219,10 +1219,7 @@ test("browser_tests") {
     # implemented. See crbug.com/611756
   ]
 
-  configs += [
-    "//build/config:precompiled_headers",
-    "//third_party/WebKit/public:debug_devtools",
-  ]
+  configs += [ "//build/config:precompiled_headers" ]
 
   deps = [
     ":browser_tests_runner",
@@ -1230,6 +1227,7 @@ test("browser_tests") {
     ":test_support",
     "//base",
     "//components/sync:test_support_model",
+    "//third_party/WebKit/public:features",
   ]
 
   data_deps = []