platform2: Move Error class from Buffet to libchromeos

Moved buffet::Error class and related facilities to
libchromeos and changed the namespace to 'chromeos::'.
Updated a bunch of code to include the header files
from the new location and referring to the new
namespace.

BUG=chromium:403604
TEST=USE=buffet ./build_packages
     FEATURES=test emerge-link libchromeos
     USE=buffet FEATURES=test emerge-link platform2

Change-Id: I0b5b37ccd7ee3b7be9467ebfae5d172d9b057cf6
Reviewed-on: https://chromium-review.googlesource.com/212525
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/commands/command_instance.h b/buffet/commands/command_instance.h
index f5d259d..a901380 100644
--- a/buffet/commands/command_instance.h
+++ b/buffet/commands/command_instance.h
@@ -10,10 +10,10 @@
 #include <string>
 
 #include <base/basictypes.h>
+#include <chromeos/error.h>
 
 #include "buffet/commands/prop_values.h"
 #include "buffet/commands/schema_utils.h"
-#include "buffet/error.h"
 
 namespace base {
 class Value;
@@ -49,7 +49,7 @@
   static std::unique_ptr<const CommandInstance> FromJson(
       const base::Value* value,
       const CommandDictionary& dictionary,
-      ErrorPtr* error);
+      chromeos::ErrorPtr* error);
 
  private:
   // Full command name as "<package_name>.<command_name>".