Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: Ic7e236a7f58c4021a3f8fb4536a6457d262fe62e
diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index e84faff..e62b80f 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -945,7 +945,7 @@
 
 class ResolveCatchBlockExceptionsClassVisitor : public ClassVisitor {
  public:
-  ResolveCatchBlockExceptionsClassVisitor(
+  explicit ResolveCatchBlockExceptionsClassVisitor(
       std::set<std::pair<uint16_t, const DexFile*>>& exceptions_to_resolve)
      : exceptions_to_resolve_(exceptions_to_resolve) {}