Add a way to turn off unique_fd's operator int.

unique_fd's implicit conversion to int has led to tons of problems (see
all of the overloads for close, fdopen, fdopendir, etc.). Add a switch
that can turn it off, and reduce the ridiculous amount of work to fix up
callers by introducing a borrowed_fd type that can be constructed from
either int or unique_fd.

Test: treehugger
Change-Id: If77cf5cbcaddacdaec5919a15b3520fb68f51a62
diff --git a/adb/shell_protocol.h b/adb/shell_protocol.h
index 2c82689..4aab813 100644
--- a/adb/shell_protocol.h
+++ b/adb/shell_protocol.h
@@ -21,6 +21,7 @@
 #include <android-base/macros.h>
 
 #include "adb.h"
+#include "adb_unique_fd.h"
 
 // Class to send and receive shell protocol packets.
 //
@@ -60,7 +61,7 @@
     // should be dynamically allocated on the heap instead.
     //
     // |fd| is an open file descriptor to be used to send or receive packets.
-    explicit ShellProtocol(int fd);
+    explicit ShellProtocol(borrowed_fd fd);
     virtual ~ShellProtocol();
 
     // Returns a pointer to the data buffer.
@@ -103,7 +104,7 @@
         kHeaderSize = sizeof(Id) + sizeof(length_t)
     };
 
-    int fd_;
+    borrowed_fd fd_;
     char buffer_[kBufferSize];
     size_t data_length_ = 0, bytes_left_ = 0;