Move strict mode checks earlier.

This avoids crashing on duplicate keys in the exports object of a goog module, and finds some strict-mode checks that were being missed before.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=162274729

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

@@ -265,6 +265,7 @@ protected List<PassFactory> getChecks() {
     }
 
     checks.add(checkVariableReferences);
+    checks.add(checkStrictMode);
 
     if (options.closurePass) {
       checks.add(closureCheckModule);
@@ -466,8 +467,6 @@ private void addNonTranspilationCheckPasses(List<PassFactory> checks) {
       checks.add(checkGlobalNames);
     }
 
-    checks.add(checkStrictMode);
-
     if (!options.getConformanceConfigs().isEmpty()) {
       checks.add(checkConformance);
     }

test/com/google/javascript/jscomp/IntegrationTest.java

@@ -2873,6 +2873,21 @@ public void testCheckStrictMode() {
     test(options, code, "", StrictModeCheck.ARGUMENTS_CALLEE_FORBIDDEN);
   }
 
+  public void testCheckStrictModeGeneratorFunction() {
+    CompilerOptions options = createCompilerOptions();
+    options.setLanguageIn(LanguageMode.ECMASCRIPT_2015);
+    options.setLanguageOut(LanguageMode.ECMASCRIPT3);
+    CompilationLevel.ADVANCED_OPTIMIZATIONS.setOptionsForCompilationLevel(options);
+    options.setWarningLevel(DiagnosticGroups.ES5_STRICT, CheckLevel.WARNING);
+
+    externs = ImmutableList.of(
+        SourceFile.fromCode("externs", "var arguments; arguments.callee;"));
+
+    String code = "function *gen() { arguments.callee; }";
+
+    test(options, code, StrictModeCheck.ARGUMENTS_CALLEE_FORBIDDEN);
+  }
+
   // http://blickly.github.io/closure-compiler-issues/#701
   public void testIssue701() {
     // Check ASCII art in license comments.
@@ -3590,6 +3605,27 @@ public void testSortingOff() {
          ProcessClosurePrimitives.LATE_PROVIDE_ERROR);
   }
 
+  public void testGoogModuleDuplicateExport() {
+    CompilerOptions options = createCompilerOptions();
+    options.setClosurePass(true);
+    options.setLanguageIn(LanguageMode.ECMASCRIPT_2015);
+    options.setLanguageOut(LanguageMode.ECMASCRIPT5);
+    options.setStrictModeInput(true);
+    options.setWarningLevel(DiagnosticGroups.ES5_STRICT, CheckLevel.ERROR);
+
+    test(
+        options,
+        LINE_JOINER.join(
+            "goog.module('example');",
+            "",
+            "class Foo {}",
+            "exports = {",
+            "  Foo,",
+            "  Foo,",
+            "};"),
+        StrictModeCheck.DUPLICATE_OBJECT_KEY);
+  }
+
   public void testGoogModuleOuterLegacyInner() {
     CompilerOptions options = new CompilerOptions();
     options.setClosurePass(true);