[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/api_signature.h

Index: extensions/renderer/bindings/api_signature.h
diff --git a/extensions/renderer/api_signature.h b/extensions/renderer/bindings/api_signature.h
similarity index 94%
rename from extensions/renderer/api_signature.h
rename to extensions/renderer/bindings/api_signature.h
index a8f3fa873a2df6b9658771b20483b0bd11cd4441..8eeee0e5586a0f9ad0b507ca50f155f82f75a651 100644
--- a/extensions/renderer/api_signature.h
+++ b/extensions/renderer/bindings/api_signature.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef EXTENSIONS_RENDERER_API_SIGNATURE_H_
-#define EXTENSIONS_RENDERER_API_SIGNATURE_H_
+#ifndef EXTENSIONS_RENDERER_BINDINGS_API_SIGNATURE_H_
+#define EXTENSIONS_RENDERER_BINDINGS_API_SIGNATURE_H_
 
 #include <memory>
 #include <string>
@@ -77,4 +77,4 @@ class APISignature {
 
 }  // namespace extensions
 
-#endif  // EXTENSIONS_RENDERER_API_SIGNATURE_H_
+#endif  // EXTENSIONS_RENDERER_BINDINGS_API_SIGNATURE_H_