External gadget titles are garbled while editing a page

Summary

External gadget titles are garbled while editing a page if the user language preference is set to Japanese.

Environment

• Confluence 5.10.7
• JIRA 7.2.3

Steps to Reproduce

1. Create an application link between Confluence and JIRA
2. Register the following JIRA gadgets
   
   • Activity Stream
   • Pie Chart
   • Issue Statistics
   • Two Dimensional Filter Statistics
3. Restart Confluence
   This step is important! If you have ever done the following steps in other languages than Japanese until the restart, you will not be reproduce this bug.
4. Change your language preference to Japanese
5. Open a page in edit mode
6. Add the above external JIRA gadgets from + (Insert more contents) > Other macros
   Do not confuse the gadgets with JIRA Macros, JIRA Chart Macros and the existing Activity Stream. The problem about the existing Activity Stream has already been reported as another bug here.

Expected Results

The gadget titles shouldn't be garbled.

Actual Results

The gadget titles were garbled as follows.

Notes

• Even though we installed appropriate fonts files in both of Confluence and JIRA with following the instruction -CONF-36557-, this problem was happened
• After saving the page, there seems to be no problem at all. All the contents was shown correctly.

Workaround

Use JIRA Macros and JIRA Chart Macros instead.