clean: remove unnecessary Cleaner constructor variant

`Cleaner` provides two constructors that are the same except that one
constructs a "real" disk interface internally and the other takes a
caller-provided disk interface.  A real disk interface is already
available at the only call site for the former constructor.  Use it
directly and drop the unnecessary constructor variant.

src/clean.cc

@@ -22,16 +22,6 @@
 #include "state.h"
 #include "util.h"
 
-Cleaner::Cleaner(State* state, const BuildConfig& config)
-  : state_(state),
-    config_(config),
-    removed_(),
-    cleaned_(),
-    cleaned_files_count_(0),
-    disk_interface_(new RealDiskInterface),
-    status_(0) {
-}
-
 Cleaner::Cleaner(State* state,
                  const BuildConfig& config,
                  DiskInterface* disk_interface)

src/clean.h

@@ -28,11 +28,7 @@ struct Rule;
 struct DiskInterface;
 
 struct Cleaner {
-  /// Build a cleaner object with a real disk interface.
-  Cleaner(State* state, const BuildConfig& config);
-
   /// Build a cleaner object with the given @a disk_interface
-  /// (Useful for testing).
   Cleaner(State* state,
           const BuildConfig& config,
           DiskInterface* disk_interface);

src/ninja.cc

@@ -651,7 +651,7 @@ int NinjaMain::ToolClean(const Options* options, int argc, char* argv[]) {
     return 1;
   }
 
-  Cleaner cleaner(&state_, config_);
+  Cleaner cleaner(&state_, config_, &disk_interface_);
   if (argc >= 1) {
     if (clean_rules)
       return cleaner.CleanRules(argc, argv);