Move MethodHelper::GetReturnType to mirror::ArtMethod.

Also, fix missing handle in HasSameSignatureWithDifferentClassLoaders.

Change-Id: I9e1ffd09be950ecc8346fc3c485760d82d9ecab3
diff --git a/runtime/mirror/art_method.h b/runtime/mirror/art_method.h
index 92b2c30..9bb838b 100644
--- a/runtime/mirror/art_method.h
+++ b/runtime/mirror/art_method.h
@@ -505,6 +505,10 @@
   const char* GetTypeDescriptorFromTypeIdx(uint16_t type_idx)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
+  // May cause thread suspension due to GetClassFromTypeIdx calling ResolveType this caused a large
+  // number of bugs at call sites.
+  mirror::Class* GetReturnType(bool resolve = true) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
   mirror::ClassLoader* GetClassLoader() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   mirror::DexCache* GetDexCache() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);