Fix google-explicit-constructor warnings in art.

* Add explicit keyword to conversion constructors,
  or NOLINT for implicit converters.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I1e1ee2661812944904fedadeff97b620506db47d
diff --git a/runtime/oat_quick_method_header.h b/runtime/oat_quick_method_header.h
index abddc6d..ee5002f 100644
--- a/runtime/oat_quick_method_header.h
+++ b/runtime/oat_quick_method_header.h
@@ -30,11 +30,11 @@
 // OatQuickMethodHeader precedes the raw code chunk generated by the compiler.
 class PACKED(4) OatQuickMethodHeader {
  public:
-  OatQuickMethodHeader(uint32_t vmap_table_offset = 0U,
-                       uint32_t frame_size_in_bytes = 0U,
-                       uint32_t core_spill_mask = 0U,
-                       uint32_t fp_spill_mask = 0U,
-                       uint32_t code_size = 0U);
+  explicit OatQuickMethodHeader(uint32_t vmap_table_offset = 0U,
+                                uint32_t frame_size_in_bytes = 0U,
+                                uint32_t core_spill_mask = 0U,
+                                uint32_t fp_spill_mask = 0U,
+                                uint32_t code_size = 0U);
 
   ~OatQuickMethodHeader();