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

cc/BUILD.gn

Index: cc/BUILD.gn
diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 7c1254aa739bf0384054011d58bd14c1237e22d7..9d7cc767813513522d746668dc08e3f7c9ad3ed7 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn
@@ -470,6 +470,7 @@ component("cc") {
     "//base",
     "//base/third_party/dynamic_annotations",
     "//gpu",
+    "//gpu/command_buffer/client:gles2_interface",
     "//media",
     "//skia",
     "//ui/events:events_base",
@@ -632,6 +633,10 @@ source_set("test_support") {
   if (!is_android) {  # TODO(GYP) Enable on Android when osmesa links.
     deps += [ "//third_party/mesa:osmesa" ]
   }
+
+  forward_dependent_configs_from = [
+    "//gpu:test_support",

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

test_context_provider.h includes gles2_interface_stub.h from //gpu:test_support.

+  ]
 }
 
 test("cc_unittests") {
@@ -764,6 +769,7 @@ test("cc_unittests") {
     "//cc/surfaces",
     "//gpu",
     "//gpu:test_support",
+    "//gpu/command_buffer/client:gles2_interface",

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

//cc doesn't forward configs for this, and I believe it shouldn't (since it's
not used in any cc headers). Adding explicit dependency here, since
renderer_pixeltest.cc uses gles2_interface.h.

     "//gpu/command_buffer/common:gles2_utils",
     "//media",
     "//testing/gmock",