enable android GetMimeTypeFromExtention in mime_util

net/base/platform_mime_util_linux.cc

Index: net/base/platform_mime_util_linux.cc
diff --git a/net/base/platform_mime_util_linux.cc b/net/base/platform_mime_util_linux.cc
index f26b453316f8666c2d59fe8e099683aa19b1e9c9..145f218aff3b80c45147e9ef8b17370c5856611e 100644
--- a/net/base/platform_mime_util_linux.cc
+++ b/net/base/platform_mime_util_linux.cc
@@ -20,13 +20,7 @@ namespace net {
 #if defined(OS_ANDROID)
 bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
     const FilePath::StringType& ext, std::string* result) const {
-  // TODO(jingzhao): Recover the original implementation once we support JNI.
-#if 0
   return android::GetMimeTypeFromExtension(ext, result);
-#else
-  NOTIMPLEMENTED();
-  return false;
-#endif
 }
 #else
 bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(