GTK: fix link button double free....

GTK: fix link button double free.

If set_normal_color was called while native_markup == normal_markup, then the string could be double freed. To fix this problem and prevent similar future mistakes, I made native_markup stdup normal_markup instead of just copying the pointer (the optimization wasn't worth the trickiness). Also, I cleaned up destruction logic.

BUG=27855
TEST=tried every flavor of chrome link button:
- classic theme
- non classic theme
- gtk theme
- gtk theme system theme that has non-default link text color property

[Evan Martin, 2009-11-17 03:00:37]

http://codereview.chromium.org/400009/diff/1/2
File chrome/browser/gtk/gtk_chrome_link_button.cc (right):

http://codereview.chromium.org/400009/diff/1/2#newcode45
Line 45: free(button->text);
g_free for consistency

http://codereview.chromium.org/400009/diff/1/2#newcode101
Line 101: button->native_markup = strdup(button->normal_markup);
use g_strdup to match the g_free above

http://codereview.chromium.org/400009/diff/1/2#newcode227
Line 227: button->text = strdup(text);
g_strdup

[Evan Martin, 2009-11-17 03:02:52]

OK

[Evan Stade, 2009-11-17 03:12:03]

updated again to use g_strdup_printf, committing when (if) tree opens