[analyzer] Factor getCalleeName to the checker context.
many checkers are trying to get a name of the callee when visiting
a CallExpr, so provide a convenience API.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144820 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/MacOSKeychainAPIChecker.cpp b/lib/StaticAnalyzer/Checkers/MacOSKeychainAPIChecker.cpp
index 6dc51a4..c9de38c 100644
--- a/lib/StaticAnalyzer/Checkers/MacOSKeychainAPIChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/MacOSKeychainAPIChecker.cpp
@@ -440,16 +440,7 @@
 void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
                                             CheckerContext &C) const {
   const ProgramState *State = C.getState();
-  const Expr *Callee = CE->getCallee();
-  SVal L = State->getSVal(Callee);
-
-  const FunctionDecl *funDecl = L.getAsFunctionDecl();
-  if (!funDecl)
-    return;
-  IdentifierInfo *funI = funDecl->getIdentifier();
-  if (!funI)
-    return;
-  StringRef funName = funI->getName();
+  StringRef funName = C.getCalleeName(CE);
 
   // If a value has been allocated, add it to the set for tracking.
   unsigned idx = getTrackedFunctionIndex(funName, true);