Fixed rounded corner javadoc rendering issue.

Bug: 183190634
Test: 1. make doc-comment-check-docs
      2. unzip doc-comment-check-docs-docs.zip in
         $ANDROID_BUILD_TOP/out/target/common/docs
      3. open RoundedCorner.html in reference/android/view/
Change-Id: Iff8d10db2fd3aaa26035e75c6acb342e5dc07a10