Modified the pepper file chooser API to support filtering files by extensions.

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 7f544a446583d638a84aa909a976f95c371dc529..feeb0a316863bfd291ae038ef6da3dc2296ad617 100644
--- a/chrome/browser/file_select_helper.h
+++ b/chrome/browser/file_select_helper.h
@@ -123,7 +123,8 @@ class FileSelectHelper
   // Helper method to get allowed extensions for select file dialog from
   // the specified accept types as defined in the spec:
   //   http://whatwg.org/html/number-state.html#attr-input-accept
-  // |accept_types| contains only valid lowercased MIME types.
+  // |accept_types| contains only valid lowercased MIME types or file extensions
+  // beginning with a period (.).
   SelectFileDialog::FileTypeInfo* GetFileTypesFromAcceptType(
       const std::vector<string16>& accept_types);