Allow to disable renaming for the JS version of the compiler.

Closes #2707

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175026611

src/com/google/javascript/jscomp/gwt/client/GwtRunner.java

@@ -37,9 +37,11 @@
 import com.google.javascript.jscomp.DiagnosticType;
 import com.google.javascript.jscomp.JSError;
 import com.google.javascript.jscomp.ModuleIdentifier;
+import com.google.javascript.jscomp.PropertyRenamingPolicy;
 import com.google.javascript.jscomp.SourceFile;
 import com.google.javascript.jscomp.SourceMap;
 import com.google.javascript.jscomp.SourceMapInput;
+import com.google.javascript.jscomp.VariableRenamingPolicy;
 import com.google.javascript.jscomp.WarningLevel;
 import com.google.javascript.jscomp.deps.ModuleLoader.ResolutionMode;
 import com.google.javascript.jscomp.deps.SourceCodeEscapers;
@@ -97,6 +99,7 @@ private static class Flags {
     boolean preserveTypeAnnotations;
     boolean processClosurePrimitives;
     boolean processCommonJsModules;
+    boolean renaming;
     public String renamePrefixNamespace;
     boolean rewritePolyfills;
     String warningLevel;
@@ -141,6 +144,7 @@ private static class Flags {
     defaultFlags.processClosurePrimitives = true;
     defaultFlags.processCommonJsModules = false;
     defaultFlags.renamePrefixNamespace = null;
+    defaultFlags.renaming = true;
     defaultFlags.rewritePolyfills = true;
     defaultFlags.warningLevel = "DEFAULT";
     defaultFlags.useTypesForOptimization = true;
@@ -333,6 +337,10 @@ private static void applyOptionsFromFlags(CompilerOptions options, Flags flags)
             "Bad value for compilationLevel: " + flags.compilationLevel);
       }
     }
+    if (level == CompilationLevel.ADVANCED_OPTIMIZATIONS && !flags.renaming) {
+      throw new RuntimeException(
+          "renaming cannot be disabled when ADVANCED_OPTMIZATIONS is used");
+    }
     level.setOptionsForCompilationLevel(options);
     if (flags.assumeFunctionWrapper) {
       level.setWrappedOutputOptimizations(options);
@@ -417,6 +425,10 @@ private static void applyOptionsFromFlags(CompilerOptions options, Flags flags)
     options.setClosurePass(flags.processClosurePrimitives);
     options.setProcessCommonJSModules(flags.processCommonJsModules);
     options.setRenamePrefixNamespace(flags.renamePrefixNamespace);
+    if (!flags.renaming) {
+      options.setVariableRenaming(VariableRenamingPolicy.OFF);
+      options.setPropertyRenaming(PropertyRenamingPolicy.OFF);
+    }
     options.setRewritePolyfills(flags.rewritePolyfills);
   }