Fix pass driver's dump_pass_list_ and print_pass_list_.

The lists were allocated with new char[], so they should
have been held by std::unique_ptr<const char[]> rather than
std::unique_ptr<const char>. However, it's much cleaner with
std::string.

Change-Id: Ie7c604773272194345f5e6e3c4803c3a914edf99
diff --git a/compiler/dex/pass_driver.h b/compiler/dex/pass_driver.h
index 788f24b..bd8f53c 100644
--- a/compiler/dex/pass_driver.h
+++ b/compiler/dex/pass_driver.h
@@ -153,12 +153,12 @@
     default_print_passes_ = true;
   }
 
-  static void SetDumpPassList(const char* list) {
-    dump_pass_list_.reset(list);
+  static void SetDumpPassList(const std::string& list) {
+    dump_pass_list_ = list;
   }
 
-  static void SetPrintPassList(const char* list) {
-    print_pass_list_.reset(list);
+  static void SetPrintPassList(const std::string& list) {
+    print_pass_list_ = list;
   }
 
   void SetDefaultPasses() {
@@ -202,10 +202,10 @@
   static bool default_print_passes_;
 
   /** @brief What are the passes we want to be printing the log messages? */
-  static std::unique_ptr<const char> print_pass_list_;
+  static std::string print_pass_list_;
 
   /** @brief What are the passes we want to be dumping the CFG? */
-  static std::unique_ptr<const char> dump_pass_list_;
+  static std::string dump_pass_list_;
 };
 
 }  // namespace art