Mojo JS bindings: make sure that console.log() could be used in the bindings.

ios/web/webui/mojo_facade.h

Index: ios/web/webui/mojo_facade.h
diff --git a/ios/web/webui/mojo_facade.h b/ios/web/webui/mojo_facade.h
index 1d6d487d01bcee75ce4a503f6a10b85d548a2b45..f0fd752e9a729f4fd97ac967bd7b698171df1bb5 100644
--- a/ios/web/webui/mojo_facade.h
+++ b/ios/web/webui/mojo_facade.h
@@ -50,6 +50,7 @@ class MojoFacade {
   //   core.readMessage (HandleCoreReadMessage)
   //   support.watch (HandleSupportWatch)
   //   support.cancelWatch (HandleSupportCancelWatch)
+  //   console.log (HandleConsoleLog)
   std::string HandleMojoMessage(const std::string& mojo_message_as_json);
 
  private:
@@ -125,6 +126,11 @@ class MojoFacade {
   std::unique_ptr<base::Value> HandleSupportCancelWatch(
       const base::DictionaryValue* args);
 
+  // Logs a message. |args| is a dictionary which must contain "message" key.
+  // Returns null.
+  std::unique_ptr<base::Value> HandleConsoleLog(
+      const base::DictionaryValue* args);
+
   // Provides interfaces.
   service_manager::mojom::InterfaceProvider* interface_provider_;
   // Runs JavaScript on WebUI page.