DevTools: top level await rewrite should not change for of var decl

We can not replace it with our regular void (a = ...) here, so let's
just ignore it.

R=lushnikov@chromium.org

Bug: chromium:805249
Change-Id: I859ca107a15a0284a7c6a2ed0e32fe0c11d4734f
Reviewed-on: https://chromium-review.googlesource.com/1249539
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594816}

third_party/WebKit/LayoutTests/http/tests/devtools/unit/preprocess-top-level-awaits-expected.txt

@@ -116,4 +116,9 @@ var {a = await new Promise(resolve => resolve({a:123}))} = {a : 3}
 was processed:
 (async () => {void ({a = await new Promise(resolve => resolve({a:123}))} = {a : 3})
 })()
+--------------
+await 1; for (var a of [1,2,3]);
+was processed:
+(async () => {await 1; for (var a of [1,2,3]);
+})()
 

third_party/WebKit/LayoutTests/http/tests/devtools/unit/preprocess-top-level-awaits.js

@@ -24,7 +24,8 @@
     'for await (const number of asyncRandomNumbers()) {}',
     '[...(await fetch(\'url\', { method: \'HEAD\' })).headers.entries()]',
     'await 1\n//hello',
-    'var {a = await new Promise(resolve => resolve({a:123}))} = {a : 3}'
+    'var {a = await new Promise(resolve => resolve({a:123}))} = {a : 3}',
+    'await 1; for (var a of [1,2,3]);'
   ];
 
   await TestRunner.loadModule("formatter");

third_party/blink/renderer/devtools/front_end/formatter_worker/FormatterWorker.js

@@ -195,6 +195,8 @@ FormatterWorker.preprocessTopLevelAwaitExpressions = function(content) {
     VariableDeclaration(node) {
       if (node.kind !== 'var' && node.parent !== body)
         return;
+      if (node.parent.type === 'ForOfStatement' && node.parent.left === node)
+        return;
       const onlyOneDeclaration = node.declarations.length === 1;
       changes.push(
           {text: onlyOneDeclaration ? 'void' : 'void (', start: node.start, end: node.start + node.kind.length});