Restrict PPAPI Win32k lockdown to Win10 and above.

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 734bd648622910c5b38e8b5d32d85f8c8f7da74b..dc4ff8dbd8d25186158892b338d1ab4449be0fca 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -2695,6 +2695,9 @@ bool ChromeContentBrowserClient::PreSpawnRenderer(
 
 bool ChromeContentBrowserClient::IsWin32kLockdownEnabledForMimeType(
     const std::string& mime_type) const {
+  // We don't support PPAPI win32k lockdown prior to Windows 10.
+  if (base::win::GetVersion() < base::win::VERSION_WIN10)
+    return false;
   // First, check if any variation parameters have enabled or disabled this
   // mime type either specifically or globally.
   std::map<std::string, std::string> mime_params;