Allow the renaming policies to be disabled by a flag.

Closes #2721

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175986804

Author: ChadKillingsworth

src/com/google/javascript/jscomp/CommandLineRunner.java

@@ -790,6 +790,11 @@ private static class Flags {
     )
     private String packageJsonEntryNames = null;
 
+    @Option(name = "--renaming",
+        handler = BooleanOptionHandler.class,
+        usage = "Disables variable renaming. Cannot be used with ADVANCED optimizations.")
+    private boolean renaming = true;
+
     @Argument
     private List<String> arguments = new ArrayList<>();
     private final CmdLineParser parser;
@@ -1559,6 +1564,12 @@ private void initConfigFromFlags(String[] args, PrintStream out, PrintStream err
         }
       }
 
+      if (!flags.renaming
+          && flags.compilationLevelParsed == CompilationLevel.ADVANCED_OPTIMIZATIONS) {
+        reportError("ERROR - renaming cannot be disabled when ADVANCED_OPTMIZATIONS is used.");
+        runCompiler = false;
+      }
+
       getCommandLineConfig()
           .setPrintTree(flags.printTree)
           .setPrintAst(flags.printAst)
@@ -1800,6 +1811,11 @@ protected CompilerOptions createOptions() {
       }
     }
 
+    if (!flags.renaming) {
+      options.setVariableRenaming(VariableRenamingPolicy.OFF);
+      options.setPropertyRenaming(PropertyRenamingPolicy.OFF);
+    }
+
     return options;
   }