Use a placeholder instead of the default plugin for missing plug-ins on Mac and Linux.

chrome/common/default_plugin.cc

Index: chrome/common/default_plugin.cc
diff --git a/chrome/common/default_plugin.cc b/chrome/common/default_plugin.cc
index 61bbc8778d7f61eacef30c33dfc5ebdef26545a6..67c2b431a1141d68effd67de7bc49d7bc8ff83cf 100644
--- a/chrome/common/default_plugin.cc
+++ b/chrome/common/default_plugin.cc
@@ -10,6 +10,10 @@
 namespace chrome {
 
 void RegisterInternalDefaultPlugin() {
+#if defined(OS_WIN)
+  // TODO(bauerb): On Windows the default plug-in can download and install
+  // missing plug-ins, which we don't support in the browser yet, so keep
+  // using the default plug-in on Windows until we do.
   const webkit::npapi::PluginEntryPoints entry_points = {
 #if !defined(OS_POSIX) || defined(OS_MACOSX)
     default_plugin::NP_GetEntryPoints,
@@ -24,6 +28,7 @@ void RegisterInternalDefaultPlugin() {
       "Provides functionality for installing third-party plug-ins",
       "*",
       entry_points);
+#endif  // defined OS(WIN)
 }
 
 }  // namespace chrome