Pass defines to grit when computing inputs for analyze.

When running `mb analyze` on the builders, we want to make
sure we correctly catch changes to files included by grit
but not explicitly mentioned as inputs in the BUILD.gn files.
Unfortunately, we weren't passing along the -D flags we're
using to actually run grit, and so we were not catching the
files that are conditionally included.

R=ddorwin@chromium.org
BUG=862731

Change-Id: I68b98e5786a2dd44e9ee5404aa4de3b0b1feaf33
Reviewed-on: https://chromium-review.googlesource.com/1150612Reviewed-by: David Dorwin <ddorwin@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578102}

tools/grit/grit_rule.gni

@@ -409,7 +409,7 @@ template("grit") {
       grit_info_args = [
                          "--inputs",
                          source_path,
-                       ] + grit_flags + grit_defines
+                       ] + grit_flags + grit_defines + define_args
 
       # Only call exec_script when the user has explicitly opted into greater
       # precision at the expense of performance.