From: Ubuntu
Subject: introduce a pref to prefer certain plugins for mime-types

diff --git a/dom/plugins/base/nsPluginHost.cpp b/dom/plugins/base/nsPluginHost.cpp
--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -1543,17 +1543,51 @@ nsPluginHost::FindPluginForType(const ch
   if (!aMimeType) {
     return nullptr;
   }
 
   LoadPlugins();
 
   InfallibleTArray<nsPluginTag*> matchingPlugins;
 
+  char *preferredPluginPath = NULL;
+  nsAutoCString mimetypePrefString ("modules.plugins.mimetype.");
+  mimetypePrefString.Append(aMimeType);
+  const char *mimetypePrefChar = mimetypePrefString.get();
+  nsAdoptingCString pluginPath = Preferences::GetCString(mimetypePrefChar);
+  preferredPluginPath = (char*) pluginPath.get();
+
   nsPluginTag *plugin = mPlugins;
+
+  if(preferredPluginPath) {
+    while (plugin) {
+      if (!aCheckEnabled || plugin->IsEnabled()) {
+        if (0 == PL_strcasecmp(plugin->mFileName.get(), preferredPluginPath) ||
+            0 == PL_strcasecmp(plugin->mFullPath.get(), preferredPluginPath)) {
+          matchingPlugins.AppendElement(plugin);
+        }
+      }
+      plugin = plugin->mNext;
+    }
+
+    // now lets search for substrings
+    plugin = mPlugins;
+    while (plugin) {
+      if (!aCheckEnabled || plugin->IsEnabled()) {
+        if (nullptr != PL_strstr(plugin->mFileName.get(), preferredPluginPath) ||
+            nullptr != PL_strstr(plugin->mFullPath.get(), preferredPluginPath)) {
+          matchingPlugins.AppendElement(plugin);
+        }
+      }
+      plugin = plugin->mNext;
+    }
+
+    return FindPreferredPlugin(matchingPlugins);
+  }
+
   while (plugin) {
     if (!aCheckEnabled || plugin->IsEnabled()) {
       int32_t mimeCount = plugin->mMimeTypes.Length();
       for (int32_t i = 0; i < mimeCount; i++) {
         if (0 == PL_strcasecmp(plugin->mMimeTypes[i].get(), aMimeType)) {
           matchingPlugins.AppendElement(plugin);
           break;
         }