Fix up code warning and errors

Discovered by new LLVM rebase.

Clean up, no functionality change.

Test: build
Bug: 37752547
Change-Id: I7df6097706e0772226dcb07611e7d044a6085421
diff --git a/runtime/gc/accounting/mod_union_table.cc b/runtime/gc/accounting/mod_union_table.cc
index 34e30c1..c416b9c 100644
--- a/runtime/gc/accounting/mod_union_table.cc
+++ b/runtime/gc/accounting/mod_union_table.cc
@@ -391,7 +391,7 @@
     uintptr_t end = start + CardTable::kCardSize;
     live_bitmap->VisitMarkedRange(start,
                                   end,
-                                  [this, callback, arg](mirror::Object* obj) {
+                                  [callback, arg](mirror::Object* obj) {
       callback(obj, arg);
     });
   }
@@ -402,7 +402,7 @@
     uintptr_t end = start + CardTable::kCardSize;
     live_bitmap->VisitMarkedRange(start,
                                   end,
-                                  [this, callback, arg](mirror::Object* obj) {
+                                  [callback, arg](mirror::Object* obj) {
       callback(obj, arg);
     });
   }
@@ -560,7 +560,7 @@
             << start << " " << *space_;
         space_->GetLiveBitmap()->VisitMarkedRange(start,
                                                   start + CardTable::kCardSize,
-                                                  [this, callback, arg](mirror::Object* obj) {
+                                                  [callback, arg](mirror::Object* obj) {
           callback(obj, arg);
         });
       });