MojoAsyncResourceHandler: Ignore Resume/OnWritable calls after error.

content/browser/loader/mojo_async_resource_handler_unittest.cc

Index: content/browser/loader/mojo_async_resource_handler_unittest.cc
diff --git a/content/browser/loader/mojo_async_resource_handler_unittest.cc b/content/browser/loader/mojo_async_resource_handler_unittest.cc
index 616f30482b5173d7b377545b4e424c2d2c7a51b9..58a48c8712e941d5b2f73256781c003052297297 100644
--- a/content/browser/loader/mojo_async_resource_handler_unittest.cc
+++ b/content/browser/loader/mojo_async_resource_handler_unittest.cc
@@ -184,6 +184,10 @@ class TestResourceController : public ResourceController {
   }
 
   void CancelWithError(int error_code) override {
+    // While cancelling more than once is legal, none of these tests should do
+    // it.
+    EXPECT_FALSE(is_cancel_with_error_called_);
+
     is_cancel_with_error_called_ = true;
     error_ = error_code;
     if (quit_closure_)