Ensure referenced catch block exceptions are in the image.

This addresses Bug: 5732744.

Change-Id: Ia9319b821f94bb27a11358f11b5473bb405277bb
diff --git a/src/object.cc b/src/object.cc
index 8d48250..c08e122 100644
--- a/src/object.cc
+++ b/src/object.cc
@@ -815,6 +815,11 @@
   return this == String::GetJavaLangString();
 }
 
+bool Class::IsThrowableClass() const {
+  Class* throwable = Runtime::Current()->GetClassLinker()->FindSystemClass("Ljava/lang/Throwable;");
+  return throwable->IsAssignableFrom(this);
+}
+
 ClassLoader* Class::GetClassLoader() const {
   return GetFieldObject<ClassLoader*>(OFFSET_OF_OBJECT_MEMBER(Class, class_loader_), false);
 }