PNaCl Dynamic Linking: Using unordered_set to disallow duplicate modules.

src/untrusted/pll_loader/pll_loader.h

Index: src/untrusted/pll_loader/pll_loader.h
diff --git a/src/untrusted/pll_loader/pll_loader.h b/src/untrusted/pll_loader/pll_loader.h
index 65577f51f7388f2abc3cc83f42b233139f181836..a033dfd72e3834937909d3f38bf8d97e8e17b781 100644
--- a/src/untrusted/pll_loader/pll_loader.h
+++ b/src/untrusted/pll_loader/pll_loader.h
@@ -5,6 +5,8 @@
 #ifndef NATIVE_CLIENT_SRC_UNTRUSTED_PLL_LOADER_PLL_LOADER_H_
 #define NATIVE_CLIENT_SRC_UNTRUSTED_PLL_LOADER_PLL_LOADER_H_ 1
 
+#include <string>
+#include <unordered_set>
 #include <vector>
 
 #include "native_client/src/untrusted/pll_loader/pll_root.h"
@@ -53,6 +55,9 @@ class ModuleSet {
   void ResolveRefs();
 
  private:
+  // An unordered set of "sonames" (to see if a module has been loaded) and the
+  // modules themselves.
+  std::unordered_set<std::string> sonames_;
   std::vector<PLLModule> modules_;
 };