Make ControlFlowAnalysis treat MODULE_BODY as a statement block

This is a prerequisite to running passes using the CFG on modules

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=230369777

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

@@ -340,6 +340,7 @@ public void visit(NodeTraversal t, Node n, Node parent) {
       case BLOCK:
       case ROOT:
       case SCRIPT:
+      case MODULE_BODY:
         handleStmtList(n);
         return;
       case FUNCTION:
@@ -545,6 +546,7 @@ private void handleStmtList(Node node) {
         case TRY:
           break;
         case ROOT:
+          // TODO(b/71873602): why is this path necessary?
           if (node.isRoot() && node.getNext() != null) {
             createEdge(node, Branch.UNCOND, node.getNext());
           }

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

@@ -266,14 +266,34 @@ private ControlFlowGraph<Node> createCfg(String input) {
   }
 
   @Test
-  public void testSimpleStatements() throws IOException {
+  public void testSimpleStatementsInScript() {
     String src = "var a; a = a; a = a";
     ControlFlowGraph<Node> cfg = createCfg(src);
     assertDownEdge(cfg, Token.SCRIPT, Token.VAR, Branch.UNCOND);
     assertCrossEdge(cfg, Token.VAR, Token.EXPR_RESULT, Branch.UNCOND);
     assertCrossEdge(cfg, Token.EXPR_RESULT, Token.EXPR_RESULT, Branch.UNCOND);
   }
 
+  @Test
+  public void testSimpleStatementsInGoogModule() {
+    String src = "goog.module('myMod'); var a; a = a; a = a";
+    ControlFlowGraph<Node> cfg = createCfg(src);
+    assertDownEdge(cfg, Token.SCRIPT, Token.MODULE_BODY, Branch.UNCOND);
+    // the EXPR_RESULT is the goog.module(...) call
+    assertDownEdge(cfg, Token.MODULE_BODY, Token.EXPR_RESULT, Branch.UNCOND);
+    assertCrossEdge(cfg, Token.EXPR_RESULT, Token.VAR, Branch.UNCOND); // goog.module() -> var a;
+  }
+
+  @Test
+  public void testSimpleStatementsInEsModule() {
+    String src = "var a; a = a; export default a;";
+    ControlFlowGraph<Node> cfg = createCfg(src);
+    assertDownEdge(cfg, Token.SCRIPT, Token.MODULE_BODY, Branch.UNCOND);
+    assertDownEdge(cfg, Token.MODULE_BODY, Token.VAR, Branch.UNCOND);
+    assertCrossEdge(cfg, Token.VAR, Token.EXPR_RESULT, Branch.UNCOND);
+    assertCrossEdge(cfg, Token.EXPR_RESULT, Token.EXPORT, Branch.UNCOND);
+  }
+
   // Test a simple IF control flow.
   @Test
   public void testSimpleIf() throws IOException {