grit: Leave a breadcrumb to crbug.com/899437 for the next time someone runs into it.

Bug: 899437
Change-Id: I25ab289eaf053f09974413431e70ec648def95f5
Reviewed-on: https://chromium-review.googlesource.com/c/1309114Reviewed-by: Dan Erat <derat@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609695}

chromeos/resources/chromeos_resources.grd

@@ -5,7 +5,7 @@
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="grit/chromeos_resources_map.cc"
-            type="gzipped_resource_file_map_source" />
+            type="gzipped_resource_map_source" />
     <output filename="grit/chromeos_resources_map.h"
             type="gzipped_resource_map_header" />
     <output filename="chromeos_resources.pak" type="data_package" />

tools/grit/grit/format/resource_map.py

@@ -144,4 +144,9 @@ def _GetItemName(item):
 
 
 def _GetItemPath(item):
-  return item.GetInputPath().replace("\\", "/")
+  path = item.GetInputPath().replace("\\", "/")
+  # resource_maps don't currently work with variables. See crbug.com/899437
+  # for why you might not need this, and if you still think you need it then
+  # comment 17 has a patch for how to make it work.
+  assert '$' not in path, 'see comment above'
+  return path