Fix scons build where the internal theme files don't exist.

tools/grit/grit/scons.py

Index: tools/grit/grit/scons.py
diff --git a/tools/grit/grit/scons.py b/tools/grit/grit/scons.py
index 849e5379dd8befb50c690411888bee410489fb66..66d2771dd4633d7b6fe511856d0f81f7aa81da4f 100644
--- a/tools/grit/grit/scons.py
+++ b/tools/grit/grit/scons.py
@@ -147,7 +147,12 @@ def _Scanner(file_node, env, path):
          node.parent.name == 'translations')):
       files.append(os.path.abspath(node.GetFilePath()))
     elif node.name == 'include':
-      files.append(node.FilenameToOpen())
+      # We depend on all resources specified in the grd file.  However, some
+      # files are only used by official builds and aren't in the public
+      # repository (e.g., the Google Chrome logo).  If the file doesn't exist,
+      # just don't add it to the file dependencies.
+      if os.path.exists(node.FilenameToOpen()):
+        files.append(node.FilenameToOpen())
 
   # Add in the grit source files.  If one of these change, we want to re-run
   # grit.