Make net::DataURL's MIME string check stricter

content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc

Index: content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc
diff --git a/content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc b/content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc
index 20ffdc74a9f725f9708b7b0cb5e643b977934811..5eec410500202c6400e5bdb0504fb1cf53b64527 100644
--- a/content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc
+++ b/content/browser/renderer_host/pepper/pepper_file_system_browser_host.cc
@@ -484,13 +484,15 @@ std::string PepperFileSystemBrowserHost::GeneratePluginId(
   // types).  If we bring this API to stable, we might have to make it more
   // general.
 
-  if (!net::IsMimeType(mime_type))
+  std::string top_level_type;
+  std::string subtype;
+  if (!net::ParseMimeTypeWithoutParameter(
+          mime_type, &top_level_type, &subtype) ||
+      !net::IsValidTopLevelMimeType(top_level_type))
     return std::string();
-  std::string output = mime_type;
 
   // Replace a slash used for type/subtype separator with an underscore.
-  // NOTE: This assumes there is only one slash in the MIME type.
-  ReplaceFirstSubstringAfterOffset(&output, 0, "/", "_");
+  std::string output = top_level_type + "_" + subtype;
 
   // Verify |output| contains only alphabets, digits, or "._-".
   for (std::string::const_iterator it = output.begin(); it != output.end();