WebUI: only crash Chrome for invalid chrome:// URLs in debug

content/browser/webui/shared_resources_data_source.cc

Index: content/browser/webui/shared_resources_data_source.cc
diff --git a/content/browser/webui/shared_resources_data_source.cc b/content/browser/webui/shared_resources_data_source.cc
index aa1289c279e19cd9f3786f02f63971e66a4ca971..7e5baf3337e384dbfac72140d9cfdeb299e0679c 100644
--- a/content/browser/webui/shared_resources_data_source.cc
+++ b/content/browser/webui/shared_resources_data_source.cc
@@ -112,12 +112,15 @@ std::string SharedResourcesDataSource::GetMimeType(
 
 #if defined(OS_WIN)
   base::FilePath file(base::UTF8ToWide(path));
-  std::string extension = base::WideToUTF8(file.FinalExtension()).substr(1);
+  std::string extension = base::WideToUTF8(file.FinalExtension());
 #else
   base::FilePath file(path);
-  std::string extension = file.FinalExtension().substr(1);
+  std::string extension = file.FinalExtension();
 #endif
 
+  if (!extension.empty())
+    extension.erase(0, 1);
+
   if (extension == "html")
     return "text/html";
 
@@ -139,7 +142,7 @@ std::string SharedResourcesDataSource::GetMimeType(
   if (extension == "woff2")
     return "application/font-woff2";
 
-  CHECK(false) << path;
+  NOTREACHED() << path;
   return "text/plain";
 }