Silence a warning in generate_policy_source_unittest.cc.

For non-CrOS, compiler gives warning regarding unused functions.

BUG=NONE

Review URL: https://codereview.chromium.org/504723003

Cr-Commit-Position: refs/heads/master@{#291680}

components/policy/core/common/generate_policy_source_unittest.cc

@@ -20,6 +20,7 @@ namespace policy {
 
 namespace {
 
+#if defined(OS_CHROMEOS)
 // Checks if two schemas are the same or not. Note that this function doesn't
 // consider restrictions on integers and strings nor pattern properties.
 bool IsSameSchema(Schema a, Schema b) {
@@ -49,6 +50,7 @@ bool IsSameSchema(Schema a, Schema b) {
     return false;
   return IsSameSchema(a.GetAdditionalProperties(), b.GetAdditionalProperties());
 }
+#endif
 
 }  // namespace