Add missing 'explicit's on single-argument constructors.

Change-Id: I1494df6e74ec16238971fb4346ba184eb61c37ab
diff --git a/src/dex_file.h b/src/dex_file.h
index 7d3fb74..453b7c2 100644
--- a/src/dex_file.h
+++ b/src/dex_file.h
@@ -233,7 +233,7 @@
         catch_all_ = false;
       }
 
-      CatchHandlerIterator(const byte* handler_data) {
+      explicit CatchHandlerIterator(const byte* handler_data) {
         current_data_ = handler_data;
         remaining_count_ = DecodeSignedLeb128(&current_data_);