Update the tracing grit GN rule

Previously this rule had a lot of custom stuff to work around the fact that the grit rule couldn't run at GN time to get the inputs and outputs. Now that the inputs are lazy, we can use the template.

R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/414623002

git-svn-id: http://src.chromium.org/svn/trunk/src/build@284948 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

secondary/tools/grit/grit_rule.gni

@@ -27,6 +27,9 @@
 #           python tools/grit/grit_info.py --outputs . path/to/your.grd
 #       And strip the leading "./" from the output files.
 #
+#   defines (optional)
+#       Extra defines to pass to grit (on top of the global grit_defines list).
+#
 #   grit_flags (optional)
 #       List of strings containing extra command-line flags to pass to Grit.
 #
@@ -261,7 +264,16 @@ template("grit") {
       "-o", rebased_output_dir,
       "--depdir", ".",
       "--depfile", rebase_path(depfile, root_build_dir),
-    ] + grit_defines + grit_flags + assert_files_flags
+    ] + grit_defines
+
+    # Add extra defines with -D flags.
+    if (defined(invoker.defines)) {
+      foreach (i, invoker.defines) {
+        args += [ "-D", i ]
+      }
+    }
+
+    args += grit_flags + assert_files_flags
 
     visibility = target_visibility