Optimizing compiler: remove unnecessary `explicit' keywords.

Change-Id: I5927fd92d53308c81e14edbd6e7d1c943bfa085b
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index be6b355..e8d19f5 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -1271,7 +1271,7 @@
 // Load a given local. The local is an input of this instruction.
 class HLoadLocal : public HExpression<1> {
  public:
-  explicit HLoadLocal(HLocal* local, Primitive::Type type)
+  HLoadLocal(HLocal* local, Primitive::Type type)
       : HExpression(type, SideEffects::None()) {
     SetRawInputAt(0, local);
   }
@@ -1589,7 +1589,7 @@
 
 class FieldInfo : public ValueObject {
  public:
-  explicit FieldInfo(MemberOffset field_offset, Primitive::Type field_type)
+  FieldInfo(MemberOffset field_offset, Primitive::Type field_type)
       : field_offset_(field_offset), field_type_(field_type) {}
 
   MemberOffset GetFieldOffset() const { return field_offset_; }