Make channel available in Java via ChromeVersionConstants.java.

chrome/version.gni

Index: chrome/version.gni
diff --git a/chrome/version.gni b/chrome/version.gni
index 771ea28541d39b6ea0373a6485e6132622b4dfbd..4a96dd653b8a686e0d694be39362fc7bf0a398ad 100644
--- a/chrome/version.gni
+++ b/chrome/version.gni
@@ -15,12 +15,16 @@
 #   output:
 #     File name of file to write.
 #
+#   extra_args:
+#     Extra arguments to pass to version.py.
+#
 #   visibility (optional)
 #
 # Example:
 #   process_version("myversion") {
 #     source = "myfile.h.in"
 #     output = "$target_gen_dir/myfile.h"
+#     extra_args = ["-e", "FOO=42"]
 #   }
 template("process_version") {
   assert(defined(invoker.source), "Source must be defined for $target_name")
@@ -53,8 +57,12 @@ template("process_version") {
       "-f", rebase_path(version_path, root_build_dir),
       "-f", rebase_path(branding_path, root_build_dir),
       "-f", rebase_path(lastchange_path, root_build_dir),
-      rebase_path(invoker.source, root_build_dir),
-      rebase_path(invoker.output, root_build_dir),
+      "-i", rebase_path(invoker.source, root_build_dir),
+      "-o", rebase_path(invoker.output, root_build_dir),
     ]
+
+    if (defined(invoker.extra_args)) {
+      args += invoker.extra_args
+    }
   }
 }