Windows: Convert mime types to lowercase in GetPlatformMimeTypeFromExtension.

net/base/platform_mime_util_win.cc

Index: net/base/platform_mime_util_win.cc
diff --git a/net/base/platform_mime_util_win.cc b/net/base/platform_mime_util_win.cc
index fcac48faab53e3c10e0b12555a2c42edf720e444..1995ddf0eedf6e4c2015fb78ca4b724e5be6b56b 100644
--- a/net/base/platform_mime_util_win.cc
+++ b/net/base/platform_mime_util_win.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/registry.h"
 
@@ -19,7 +20,7 @@ bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
   base::win::RegKey(HKEY_CLASSES_ROOT, key.c_str(), KEY_READ).ReadValue(
       L"Content Type", &value);
   if (!value.empty()) {
-    *result = base::WideToUTF8(value);
+    *result = base::ToLowerASCII(base::WideToUTF8(value));
     return true;
   }
   return false;