FontPlatformDataCache uses OwnPtr instead of raw pointer.
FontPlatformDataCache uses OwnPtr instead of raw pointer.

HashMap can handle OwnPtr, so we don't have to delete an element in HashMap
manually.

Review URL: https://codereview.chromium.org/26864002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@159453 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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