This commit fixes a crash in the Angular Kythe indexer caused by failure
to retrieve `SourceFile` in a `Statement`.
Crash logs:
TypeError: Cannot read property 'text' of undefined
at Object.getTokenPosOfNode (typescript/stable/lib/typescript.js:8957:72)
at NodeObject.getStart (typescript/stable/lib/typescript.js:121419:23)
at NodeObject.getLeadingTriviaWidth (typescript/stable/lib/typescript.js:121439:25)
at FactoryGenerator.generate (angular2/rc/packages/compiler-cli/src/ngtsc/shims/src/factory_generator.ts:64:49)
at GeneratedShimsHostWrapper.getSourceFile (angular2/rc/packages/compiler-cli/src/ngtsc/shims/src/host.ts:88:26)
at findSourceFile (typescript/stable/lib/typescript.js:90654:29)
at typescript/stable/lib/typescript.js:90553:85
at getSourceFileFromReferenceWorker (typescript/stable/lib/typescript.js:90520:34)
at processSourceFile (typescript/stable/lib/typescript.js:90553:13)
at processRootFile (typescript/stable/lib/typescript.js:90383:13)
PR Close#33588