AIX: Fix 'may be used uninitialized' compiler errors

src/layout-descriptor-inl.h

Index: src/layout-descriptor-inl.h
diff --git a/src/layout-descriptor-inl.h b/src/layout-descriptor-inl.h
index 31ab5d1dd7d39b274c92c1e69f01d25c10b17652..3f150658e7f6628a517b7708113d5cc9162cff4c 100644
--- a/src/layout-descriptor-inl.h
+++ b/src/layout-descriptor-inl.h
@@ -62,8 +62,8 @@ LayoutDescriptor* LayoutDescriptor::SetRawData(int field_index) {
 
 
 LayoutDescriptor* LayoutDescriptor::SetTagged(int field_index, bool tagged) {
-  int layout_word_index;
-  int layout_bit_index;
+  int layout_word_index = 0;
+  int layout_bit_index = 0;
 
   if (!GetIndexes(field_index, &layout_word_index, &layout_bit_index)) {
     CHECK(false);