Optimizing compiler: remove unnecessary `explicit' keywords.

Change-Id: I5927fd92d53308c81e14edbd6e7d1c943bfa085b
diff --git a/compiler/optimizing/locations.h b/compiler/optimizing/locations.h
index 06623b6..8c9d416 100644
--- a/compiler/optimizing/locations.h
+++ b/compiler/optimizing/locations.h
@@ -310,7 +310,7 @@
     kCall
   };
 
-  explicit LocationSummary(HInstruction* instruction, CallKind call_kind = kNoCall);
+  LocationSummary(HInstruction* instruction, CallKind call_kind = kNoCall);
 
   void SetInAt(uint32_t at, Location location) {
     inputs_.Put(at, location);