fuchsia: Use new, qualified error names, disable old names.

build/config/fuchsia/BUILD.gn

Index: build/config/fuchsia/BUILD.gn
diff --git a/build/config/fuchsia/BUILD.gn b/build/config/fuchsia/BUILD.gn
index cf16b6fbdc662fade41a4ae1e52fc8c802bd986f..48433765d47e48d5810b83c067e8c1a4b9a3e266 100644
--- a/build/config/fuchsia/BUILD.gn
+++ b/build/config/fuchsia/BUILD.gn
@@ -9,7 +9,14 @@ assert(is_fuchsia)
 assert(is_posix)
 
 config("compiler") {
-  defines = [ "SYSROOT_VERSION=$sysroot_version" ]
+  defines = [
+    # To force full builds after sysroot updates.
+    "SYSROOT_VERSION=$sysroot_version",
+
+    # Don'have include error codes that aren't prefixed with MX_ in

[scottmg, 2017/06/16 16:57:20]

"Don'have"

(kulakowski said he was hoping to purge the old names today, so we should be
able to remove this next week after another roll.)

[Nico, 2017/06/16 17:23:26]

Done.

+    # magenta/errors.h, for they collide with ERR_ defines in chrome code.
+    "USE_MX_ERRORS",
+  ]
   cflags = []
   ldflags = []
   if (current_cpu == "arm64") {