C bindings: Implement _Validate(), and some pre-requisites

mojo/public/cpp/bindings/tests/BUILD.gn

Index: mojo/public/cpp/bindings/tests/BUILD.gn
diff --git a/mojo/public/cpp/bindings/tests/BUILD.gn b/mojo/public/cpp/bindings/tests/BUILD.gn
index 143ab490bcbfb5f3dae66e0c3efcbcee59c63635..4bbbc3f4dda8e5e96b5c0634185b6397ce36ee10 100644
--- a/mojo/public/cpp/bindings/tests/BUILD.gn
+++ b/mojo/public/cpp/bindings/tests/BUILD.gn
@@ -48,6 +48,7 @@ mojo_sdk_source_set("tests") {
 
   deps = [
     ":mojo_public_bindings_test_utils",
+    ":validation_util",
     "//testing/gtest",
   ]
 
@@ -95,6 +96,25 @@ mojo_sdk_source_set("mojo_public_bindings_test_utils") {
   mojo_sdk_deps = [ "mojo/public/c/system" ]
 }
 
+mojo_sdk_source_set("validation_util") {

[viettrungluu, 2016/07/28 23:03:01]

Do you really need a separate target here, instead of moving it into the
mojo_public_bindings_test_utils target above?

[vardhan, 2016/07/29 21:29:22]

yeah, i tried this initially :( mojo_public_bindings_test_utils is used by other
languages (cython) to parse validation test+golden files. And since this target
has some gtest references, it would force mojo_public_bindings_test_utils to be
testonly, which created some problems for cython.  It was much cleaner to just
do this (or remove gtest dependencies, which means we lose some ADD_FAILURES()
which i think we should keep)

[viettrungluu, 2016/08/01 21:17:19]

Blech. Not having a gtest dependency seems reasonable, but it seems to me that
whatever cython target is depending on mojo_public_bindings_test_utils should be
testonly (and so should mojo_public_bindings_test_utils). Could you add a TODO
about this?

[vardhan, 2016/08/01 22:18:16]

Done.

+  testonly = true
+
+  sources = [
+    "validation_util.cc",
+    "validation_util.h",
+  ]
+
+  mojo_sdk_deps = [
+    "mojo/public/c/system",
+    "mojo/public/cpp/test_support",
+  ]
+
+  deps = [
+    ":mojo_public_bindings_test_utils",
+    "//testing/gtest",
+  ]
+}
+
 mojo_native_application("versioning_test_service") {
   testonly = true