Bug 549989 - Add cast for CompilationUnitContext

Since the return type of CompilationUnitContextType.createContext()
changed
to DocumentTemplateContext, so a cast is needed to avoid build error.

More information, check: https://git.eclipse.org/r/#/c/147755/.

Change-Id: Iaaa5104296e06fcef989728efa75f60b24cf5129
Signed-off-by: Sheng Chen <sheche@microsoft.com>
3 files changed