Reenable CRWJSPOSTRequestLoaderTest.LoadsCorrectHTML.

The test was flaky on iOS 9 device bots that we don't have anymore.

Bug: 591379
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I21dc7f3a76739a82b77ee1a5d7fd920cc419545e
Reviewed-on: https://chromium-review.googlesource.com/836595Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525319}

ios/web/web_state/js/crw_js_post_request_loader_unittest.mm

@@ -36,15 +36,7 @@ NSString* const kBlobToBase64StringScript =
      "  };"
      "};";
 
-// Tests that the POST request is correctly executed through XMLHttpRequest.
-// TODO(crbug.com/592034): This test is flaky on device.
-#if TARGET_IPHONE_SIMULATOR
-#define MAYBE_LoadsCorrectHTML LoadsCorrectHTML
-#else
-#define MAYBE_LoadsCorrectHTML DISABLED_LoadsCorrectHTML
-#endif
-
-TEST_F(CRWJSPOSTRequestLoaderTest, MAYBE_LoadsCorrectHTML) {
+TEST_F(CRWJSPOSTRequestLoaderTest, LoadsCorrectHTML) {
   // Set up necessary objects.
   CRWJSPOSTRequestLoader* loader = [[CRWJSPOSTRequestLoader alloc] init];
   WKWebView* web_view = web::BuildWKWebView(CGRectZero, GetBrowserState());