Revert of Add precompiled headers to GN build for large targets.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 01eba21380ea667c3c712a2820182a2633f8abb7..75caf92173c2272b6c22cbab64eea80e66343916 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -78,12 +78,8 @@
     "NET_IMPLEMENTATION",
   ]
 
-  configs += [
-    "//build/config:precompiled_headers",
-
-    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    "//build/config/compiler:no_size_t_to_int_warning",
-  ]
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
   public_configs = [ ":net_config" ]
   include_dirs = []
 
@@ -692,12 +688,8 @@
     "url_request/url_request_test_util.h",
   ]
 
-  configs += [
-    "//build/config:precompiled_headers",
-
-    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    "//build/config/compiler:no_size_t_to_int_warning",
-  ]
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   public_deps = [
     "//base",
@@ -1320,12 +1312,8 @@
   test("net_unittests") {
     sources = gypi_values.net_test_sources
 
-    configs += [
-      "//build/config:precompiled_headers",
-
-      # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-      "//build/config/compiler:no_size_t_to_int_warning",
-    ]
+    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+    configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
     defines = []
 
     deps = [