Fix new leak in LauncherButton Fixes http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20UI%20%28valgrind%29%288%29/builds/1350/steps/memory%20test%3A%20unit/logs/A101C11CC97B99B5
Fix new leak in LauncherButton
Fixes http://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20OS%20UI%20%28valgrind%29%288%29/builds/1350/steps/memory%20test%3A%20unit/logs/A101C11CC97B99B5

BUG=None
TEST=None
TBR=sky

Review URL: https://chromiumcodereview.appspot.com/9663041

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@126044 0039d316-1c4b-4281-b951-d872f2087c98

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