Fix memory stomping by ImageLoadingTracker in BrowserActionButton.
Fix memory stomping by ImageLoadingTracker in BrowserActionButton.

In the views code, tracker_ is set to null in this case.  Without
this, I get lots of random crashes when I have 2 page actions
installed (buildbot extension and google tasks extension) and I open
close lots of windows.

BUG=26751,25558

Review URL: http://codereview.chromium.org/379020

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@31534 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser