[libclang/codecompletion] Make sure the top-level decl hash takes into account ImportDecls.

The top-level hash is used to determine if we need to update the global code-completion results.
ImportDecls did not affect the hash so a newly introduced ImportDecl would not trigger an update of the global results.

rdar://14202797

llvm-svn: 184782

clang/lib/Frontend/ASTUnit.cpp

@@ -884,7 +884,15 @@ void AddTopLevelDeclarationToHash(Decl *D, unsigned &Hash) {
       Hash = llvm::HashString(NameStr, Hash);
     }
     return;
-  }  
+  }
+
+  if (ImportDecl *ImportD = dyn_cast<ImportDecl>(D)) {
+    if (Module *Mod = ImportD->getImportedModule()) {
+      std::string ModName = Mod->getFullModuleName();
+      Hash = llvm::HashString(ModName, Hash);
+    }
+    return;
+  }
 }
 
 class TopLevelDeclTrackerConsumer : public ASTConsumer {