[jnimarshalmethod-gen] Do not miss registered methods (#357)

Fixes: #356

`Extensions.CheckMethod()` implicitly required that assemblies being
processed contained debug symbols, because it used
`ParameterDefinition.Name` in order to associate the `name` parameter
of the `[Register]` custom attribute with the Java-side name.
(`ParameterDefinition.Name` was via
`registerAttribute.Constructor.Parameters`.)

The problem is that if an assembly *doesn't* contain debug symbols,
then `ParameterDefinition.Name` may be empty, meaning we may
*skip over* methods with `[Register]` attributes.

This in turn means that those methods won't be registered, which can
result in a runtime crash.  For example:

	I/mono-stdout( 2532): Registering JNI marshal methods in Xamarin.Forms.Platform.Android.CellAdapter
	W/art     ( 2532): Attempt to remove index outside index area (6 vs 7-7)
	W/art     ( 2532): JNI WARNING: DeleteLocalRef(0x1bf00019) failed to find entry

The "traditional" Xamarin.Android Java Callable Wrapper describes 10
methods to register for this type:

	__md_methods =
	  "n_onItemLongClick:(Landroid/widget/AdapterView;Landroid/view/View;IJ)Z:GetOnItemLongClick_Landroid_widget_AdapterView_Landroid_view_View_IJHandler:Android.Widget.AdapterView/IOnItemLongClickListenerInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onActionItemClicked:(Landroid/view/ActionMode;Landroid/view/MenuItem;)Z:GetOnActionItemClicked_Landroid_view_ActionMode_Landroid_view_MenuItem_Handler:Android.Views.ActionMode/ICallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onCreateActionMode:(Landroid/view/ActionMode;Landroid/view/Menu;)Z:GetOnCreateActionMode_Landroid_view_ActionMode_Landroid_view_Menu_Handler:Android.Views.ActionMode/ICallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onDestroyActionMode:(Landroid/view/ActionMode;)V:GetOnDestroyActionMode_Landroid_view_ActionMode_Handler:Android.Views.ActionMode/ICallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onPrepareActionMode:(Landroid/view/ActionMode;Landroid/view/Menu;)Z:GetOnPrepareActionMode_Landroid_view_ActionMode_Landroid_view_Menu_Handler:Android.Views.ActionMode/ICallbackInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onItemClick:(Landroid/widget/AdapterView;Landroid/view/View;IJ)V:GetOnItemClick_Landroid_widget_AdapterView_Landroid_view_View_IJHandler:Android.Widget.AdapterView/IOnItemClickListenerInvoker, Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null\n" +
	  "n_onActionItemClicked:(Landroid/support/v7/view/ActionMode;Landroid/view/MenuItem;)Z:GetOnActionItemClicked_Landroid_support_v7_view_ActionMode_Landroid_view_MenuItem_Handler:Android.Support.V7.View.ActionMode/ICallbackInvoker, Xamarin.Android.Support.v7.AppCompat\n" +
	  "n_onCreateActionMode:(Landroid/support/v7/view/ActionMode;Landroid/view/Menu;)Z:GetOnCreateActionMode_Landroid_support_v7_view_ActionMode_Landroid_view_Menu_Handler:Android.Support.V7.View.ActionMode/ICallbackInvoker, Xamarin.Android.Support.v7.AppCompat\n" +
	  "n_onDestroyActionMode:(Landroid/support/v7/view/ActionMode;)V:GetOnDestroyActionMode_Landroid_support_v7_view_ActionMode_Handler:Android.Support.V7.View.ActionMode/ICallbackInvoker, Xamarin.Android.Support.v7.AppCompat\n" +
	  "n_onPrepareActionMode:(Landroid/support/v7/view/ActionMode;Landroid/view/Menu;)Z:GetOnPrepareActionMode_Landroid_support_v7_view_ActionMode_Landroid_view_Menu_Handler:Android.Support.V7.View.ActionMode/ICallbackInvoker, Xamarin.Android.Support.v7.AppCompat\n" +
	  "";

Meanwhile, `jnimarshalmethod-gen.exe` only finds and generates *6*:

	[JniAddNativeMethodRegistration]
	public static void __RegisterNativeMembers (JniNativeMethodRegistrationArguments args)
	{
	  Console.WriteLine ("Registering JNI marshal methods in Xamarin.Forms.Platform.Android.CellAdapter");
	  args.AddRegistrations (new JniNativeMethodRegistration[6] {
	      new JniNativeMethodRegistration ("n_onActionItemClicked", "(Landroid/view/ActionMode;Landroid/view/MenuItem;)Z", new Func<IntPtr, IntPtr, IntPtr, IntPtr, bool> (__<$>_jni_marshal_methods.n_onActionItemClicked_Landroid_view_ActionMode_Landroid_view_MenuItem_)),
	      new JniNativeMethodRegistration ("n_onCreateActionMode", "(Landroid/view/ActionMode;Landroid/view/Menu;)Z", new Func<IntPtr, IntPtr, IntPtr, IntPtr, bool> (__<$>_jni_marshal_methods.n_onCreateActionMode_Landroid_view_ActionMode_Landroid_view_Menu_)),
	      new JniNativeMethodRegistration ("n_onDestroyActionMode", "(Landroid/view/ActionMode;)V", new Action<IntPtr, IntPtr, IntPtr> (__<$>_jni_marshal_methods.n_onDestroyActionMode_Landroid_view_ActionMode_)),
	      new JniNativeMethodRegistration ("n_onPrepareActionMode", "(Landroid/view/ActionMode;Landroid/view/Menu;)Z", new Func<IntPtr, IntPtr, IntPtr, IntPtr, bool> (__<$>_jni_marshal_methods.n_onPrepareActionMode_Landroid_view_ActionMode_Landroid_view_Menu_)),
	      new JniNativeMethodRegistration ("n_onItemClick", "(Landroid/widget/AdapterView;Landroid/view/View;IJ)V", new Action<IntPtr, IntPtr, IntPtr, IntPtr, IntPtr, IntPtr> (__<$>_jni_marshal_methods.n_onItemClick_Landroid_widget_AdapterView_Landroid_view_View_IJ)),
	      new JniNativeMethodRegistration ("n_onItemLongClick", "(Landroid/widget/AdapterView;Landroid/view/View;IJ)Z", new Func<IntPtr, IntPtr, IntPtr, IntPtr, float, float, bool> (__<$>_jni_marshal_methods.n_onItemLongClick_Landroid_widget_AdapterView_Landroid_view_View_IJ))
	  });
	}

It's this mismatch which causes the runtime crash, and fixing
`Extensions.CheckMethod()` to not require debug symbols allows all
the methods to be found.

Author: radekdoulik

tools/jnimarshalmethod-gen/App.cs

@@ -251,6 +251,9 @@ void CreateMarshalMethodAssembly (string path)
 					continue;
 				}
 
+				if (Verbose)
+					ColorWriteLine ($"Processing {type} type", ConsoleColor.Yellow);
+
 				var registrationElements    = new List<Expression> ();
 				var targetType              = Expression.Variable (typeof(Type), "targetType");
 				TypeBuilder dt = null;
@@ -491,6 +494,15 @@ static bool CheckMethod (MethodDefinition m, ref string name, ref string methodN
 
 				}
 
+				if ((string.IsNullOrEmpty (name) || string.IsNullOrEmpty (signature)) && constructorArguments.Length != 3)
+					continue;
+
+				if (string.IsNullOrEmpty (name))
+					name = constructorArguments [0].Value.ToString ();
+
+				if (string.IsNullOrEmpty (signature))
+					signature = constructorArguments [1].Value.ToString ();
+
 				if (string.IsNullOrEmpty (name) || string.IsNullOrEmpty (signature))
 					continue;