GN: Create a :gles2_interface target to resolve some check errors in //cc.

gpu/BUILD.gn

Index: gpu/BUILD.gn
diff --git a/gpu/BUILD.gn b/gpu/BUILD.gn
index 7c8acc8f63ee83cc0cb444d6b72a398e25a4686b..da288206e0d25b58f2c3b999059bb8dd3b7c2469 100644
--- a/gpu/BUILD.gn
+++ b/gpu/BUILD.gn
@@ -55,14 +55,16 @@ source_set("test_support") {
     "command_buffer/client/gles2_interface_stub.h",
   ]
 
-  configs += [ "//third_party/khronos:khronos_headers" ]
-
   deps = [
     ":gpu",
+    "//gpu/command_buffer/client:gles2_interface",

[jbroman, 2014/08/13 19:27:16]

used in gles2_interface_stub.h, which is public (used in
texture_uploader_unittest.cc, for instance)

     "//testing/gmock",
     "//testing/gtest",
     "//ui/gl:gl_unittest_utils",
   ]
+  forward_dependent_configs_from = [
+    "//gpu/command_buffer/client:gles2_interface",

[jbroman, 2014/08/13 19:27:16]

gles2_interface_stub.h includes gles2_interface.h

+  ]
 }
 
 test("gl_tests") {