Issues when being called after adding many markers

[GoogleCodeExporter]

Demo link or sample code:
[Enter the URL pointing to a simple demo which clearly reproduces the bug,
or insert code snippet]

What steps will reproduce the problem?
1. Add about 500 markers in a loop.
2. Immediately after the loop block, initiate the MarkerClusterer.
3. Click on a marker; it should appear properly.
4. Click on a second marker; it will bring up the location of the first marker.
5. Click on the second marker again; it will show the correct location after 
clicking on it again.

Expected result:
Clicking on the second marker the first time should bring up the location of 
the second marker.

Actual result:
It brings up the location of the first marker.

Version: 2.1.1

Browser / Operating System:
Google Chrome 47 / Windows 7 32-bit

Additional comments:
It appears when creating the marker cluster immediately after adding a lot of 
markers in a loop, the map sometimes has unpredicable behavior as described 
above.

*********************************************************
Tip: Star this issue (next to title) to receive notifications of status
changes against this issue, also used as a gauge for how many people are
interested in seeing it resolved.
*********************************************************

Original issue reported on code.google.com by thd...@gmail.com on 22 Oct 2015 at 11:39