[analyzer] Refactor checkers to use helper function for getting callee Decl and name.

We are getting name of the called function or it's declaration in a few checkers. Refactor them to use the helper function in the CheckerContext. 

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145576 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/ChrootChecker.cpp b/lib/StaticAnalyzer/Checkers/ChrootChecker.cpp
index 2f3ff26..fa79f21 100644
--- a/lib/StaticAnalyzer/Checkers/ChrootChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/ChrootChecker.cpp
@@ -62,10 +62,7 @@
 } // end anonymous namespace
 
 bool ChrootChecker::evalCall(const CallExpr *CE, CheckerContext &C) const {
-  const ProgramState *state = C.getState();
-  const Expr *Callee = CE->getCallee();
-  SVal L = state->getSVal(Callee);
-  const FunctionDecl *FD = L.getAsFunctionDecl();
+  const FunctionDecl *FD = C.getCalleeDecl(CE);
   if (!FD)
     return false;
 
@@ -125,10 +122,7 @@
 
 // Check the jail state before any function call except chroot and chdir().
 void ChrootChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
-  const ProgramState *state = C.getState();
-  const Expr *Callee = CE->getCallee();
-  SVal L = state->getSVal(Callee);
-  const FunctionDecl *FD = L.getAsFunctionDecl();
+  const FunctionDecl *FD = C.getCalleeDecl(CE);
   if (!FD)
     return;
 
@@ -143,7 +137,7 @@
     return;
   
   // If jail state is ROOT_CHANGED, generate BugReport.
-  void *const* k = state->FindGDM(ChrootChecker::getTag());
+  void *const* k = C.getState()->FindGDM(ChrootChecker::getTag());
   if (k)
     if (isRootChanged((intptr_t) *k))
       if (ExplodedNode *N = C.addTransition()) {