Remove unused FileDescriptor::Reset().

The Reset() method was not directly used anywhere.

Bug: 34284069
Test: Ran unittests. grep for 'Reset()' in update_engine.

Change-Id: I8db0f17c43a36b03acbc22cdfa35a3e6042c3e75
diff --git a/payload_consumer/file_descriptor.cc b/payload_consumer/file_descriptor.cc
index 8a23dea..ebe4428 100644
--- a/payload_consumer/file_descriptor.cc
+++ b/payload_consumer/file_descriptor.cc
@@ -127,12 +127,8 @@
   CHECK_GE(fd_, 0);
   if (IGNORE_EINTR(close(fd_)))
     return false;
-  Reset();
-  return true;
-}
-
-void EintrSafeFileDescriptor::Reset() {
   fd_ = -1;
+  return true;
 }
 
 }  // namespace chromeos_update_engine
diff --git a/payload_consumer/file_descriptor.h b/payload_consumer/file_descriptor.h
index 7bb2974..c8a5b15 100644
--- a/payload_consumer/file_descriptor.h
+++ b/payload_consumer/file_descriptor.h
@@ -39,12 +39,6 @@
 // * Write() returns the number of bytes written: this appears to be more useful
 //   for clients, who may wish to retry or otherwise do something useful with
 //   the remaining data that was not written.
-//
-// * Provides a Reset() method, which will force to abandon a currently open
-//   file descriptor and allow opening another file, without necessarily
-//   properly closing the old one. This may be useful in cases where a "closer"
-//   class does not care whether Close() was successful, but may need to reuse
-//   the same file descriptor again.
 
 namespace chromeos_update_engine {
 
@@ -98,10 +92,6 @@
   // errno accordingly.
   virtual bool Close() = 0;
 
-  // Resets the file descriptor, abandoning a currently open file and returning
-  // the descriptor to the closed state.
-  virtual void Reset() = 0;
-
   // Indicates whether or not an implementation sets meaningful errno.
   virtual bool IsSettingErrno() = 0;
 
@@ -129,7 +119,6 @@
                 uint64_t length,
                 int* result) override;
   bool Close() override;
-  void Reset() override;
   bool IsSettingErrno() override {
     return true;
   }