[SafeBrowsing] Block dangerous unchecked downloads based on a Finch trial.

chrome/browser/file_select_helper.h

Index: chrome/browser/file_select_helper.h
diff --git a/chrome/browser/file_select_helper.h b/chrome/browser/file_select_helper.h
index 0067b8a11c5c4b804068fa930a83f4ce4089c568..f3f1266b437efd657dbb5c640c7e4b9ede214def 100644
--- a/chrome/browser/file_select_helper.h
+++ b/chrome/browser/file_select_helper.h
@@ -51,6 +51,7 @@ class FileSelectHelper : public base::RefCountedThreadSafe<FileSelectHelper>,
   friend class base::RefCountedThreadSafe<FileSelectHelper>;
   FRIEND_TEST_ALL_PREFIXES(FileSelectHelperTest, IsAcceptTypeValid);
   FRIEND_TEST_ALL_PREFIXES(FileSelectHelperTest, ZipPackage);
+  FRIEND_TEST_ALL_PREFIXES(FileSelectHelperTest, GetSanitizedFileName);
   explicit FileSelectHelper(Profile* profile);
   ~FileSelectHelper() override;
 
@@ -177,6 +178,22 @@ class FileSelectHelper : public base::RefCountedThreadSafe<FileSelectHelper>,
   // no whitespace.
   static bool IsAcceptTypeValid(const std::string& accept_type);
 
+  // Get a sanitized filename suitable for use as a default filename. The
+  // suggested filename coming over the IPC may contain invalid characters or
+  // may result in a filename that's reserved on the current platform.
+  //
+  // If |suggested_path| is empty, the return value is also empty.
+  //
+  // If |suggested_path| is non-empty, but can't be safely converted to UTF-8,
+  // or is entirely lost during the sanitization process (e.g. because it
+  // consists entirely of invalid characters), it's replaced with a default
+  // filename.
+  //
+  // Otherwise, returns |suggested_path| with any invalid characters will be
+  // replaced with a suitable replacement character.
+  static base::FilePath GetSanitizedFileName(
+      const base::FilePath& suggested_path);
+
   // Profile used to set/retrieve the last used directory.
   Profile* profile_;