GN: Only define UNIT_TEST in direct gtest deps

This matches the gyp build and is important for parts of the code that
guard their API with UNIT_TEST. For instance,
chrome/browser/ui/views/omnibox/omnibox_view_views.h has a GetRenderText
function guarded by #if UNIT_TEST that shadows a protected function
GetRenderText from its parent class views::Textfield, but with different
const-ness. If c/b/u/v/o/omnibox_view_views.cc is compiled with UNIT_TEST
set, it attempts to use the guarded member function instead of the base
class which fails to compile.

R=brettw@chromium.org

Review URL: https://codereview.chromium.org/464503003

Cr-Commit-Position: refs/heads/master@{#288988}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288988 0039d316-1c4b-4281-b951-d872f2087c98

build/secondary/testing/gtest/BUILD.gn

@@ -9,7 +9,6 @@ config("gtest_config") {
   ]
 
   defines = [
-    "UNIT_TEST",
 
     # In order to allow regex matches in gtest to be shared between Windows
     # and other systems, we tell gtest to always use it's internal engine.
@@ -54,6 +53,11 @@ config("gtest_config") {
   }
 }
 
+config("gtest_direct_config") {
+  visibility = ":*"
+  defines = [ "UNIT_TEST" ]
+}
+
 static_library("gtest") {
   sources = [
     "include/gtest/gtest-death-test.h",
@@ -100,6 +104,7 @@ static_library("gtest") {
   include_dirs = [ "." ]
 
   all_dependent_configs = [ ":gtest_config" ]
+  direct_dependent_configs = [ ":gtest_direct_config" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]