To enable the Flash Content Debugger Plugin on Google Chrome. Simple disable the plugin distributed with Chrome. Of course, you'll also need to install the content debugger version of the plugin as well.
To disable the plugin distributed with Chrome open your Preferences and select the tab entitled "Under the Hood":
Then open Content Settings:
Now click on the link "Disable Individual Plugins":
On the plugins page both the plugin distributed with Chrome and the plugin installed from Adobe are listed. Simply disable the plugin located within the Chrome files at the location:
/Applications/Google Chrome.app/Contents/Versions/5.0.375.127/Flash Player Plugin for Chrome.plugin
On PC the distributed plugin can be disabled by opening the +Details button in the upper right and then disabling the plugin individually.