Fuchsia: Fix PostMessage message buffering, add & fix FrameImpl tests.

* Fixes issue with an on-receive callback not being unbound, causing
  the incoming message buffer to be drained immediately.
* Add browser tests to verify buffering behavior.
* Add browser tests to verify proper origin enforcement for
  Frame::PostMessage.
* Make the AsyncValueReceiver interface a bit nicer to use.
* Minor cleanups for other FrameImpl browser tests.

Bug: 893236
Change-Id: I521e9316ccf9195133a940be670556a882cb1044
Reviewed-on: https://chromium-review.googlesource.com/c/1351777
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612812}

webrunner/browser/message_port_impl.cc

@@ -112,7 +112,7 @@ MessagePortImpl::MessagePortImpl(mojo::ScopedMessagePipeHandle mojo_port)
   connector_->set_connection_error_handler(
       base::BindOnce(&MessagePortImpl::OnDisconnected, base::Unretained(this)));
   binding_.set_error_handler([this](zx_status_t status) {
-    if (status != ZX_OK)
+    if (status != ZX_OK && status != ZX_ERR_PEER_CLOSED)
       ZX_DLOG(INFO, status) << "Disconnected";
 
     OnDisconnected();
@@ -135,6 +135,7 @@ void MessagePortImpl::PostMessage(chromium::web::WebMessage message,
     return;
   }
   CHECK(connector_->Accept(&mojo_message));
+  callback(true);
 }
 
 void MessagePortImpl::ReceiveMessage(ReceiveMessageCallback callback) {
@@ -148,7 +149,8 @@ void MessagePortImpl::MaybeDeliverToClient() {
   if (!pending_client_read_cb_ || message_queue_.empty())
     return;
 
-  std::move(pending_client_read_cb_)(std::move(message_queue_.front()));
+  base::ResetAndReturn(&pending_client_read_cb_)(
+      std::move(message_queue_.front()));
   message_queue_.pop_front();
 }
 

webrunner/browser/test_common.h

@@ -5,6 +5,7 @@
 #ifndef WEBRUNNER_BROWSER_TEST_COMMON_H_
 #define WEBRUNNER_BROWSER_TEST_COMMON_H_
 
+#include "base/optional.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "webrunner/fidl/chromium/web/cpp/fidl.h"
@@ -45,6 +46,46 @@ class MockNavigationObserver : public chromium::web::NavigationEventObserver,
   DISALLOW_COPY_AND_ASSIGN(MockNavigationObserver);
 };
 
+// Stores an asynchronously generated value for later retrieval, optionally
+// invoking a callback on value receipt for controlling test flow.
+//
+// The value can be read by using the dereference (*) or arrow (->) operators.
+// Values must first be received before they can be accessed. Dereferencing a
+// value before it is set will produce a CHECK violation.
+template <typename T>
+class Promise {
+ public:
+  explicit Promise(base::RepeatingClosure on_capture = base::DoNothing())
+      : on_capture_(std::move(on_capture)) {}
+  ~Promise() = default;
+
+  // Returns a fit::function<> which will receive and store a value T.
+  fit::function<void(T)> GetReceiveCallback() {
+    return [this](T value) {
+      captured_ = std::move(value);
+      on_capture_.Run();
+    };
+  }
+
+  bool has_value() const { return captured_.has_value(); };
+
+  T& operator*() {
+    CHECK(captured_.has_value());
+    return *captured_;
+  }
+
+  T* operator->() {
+    CHECK(captured_.has_value());
+    return &*captured_;
+  }
+
+ private:
+  base::Optional<T> captured_;
+  base::RepeatingClosure on_capture_;
+
+  DISALLOW_COPY_AND_ASSIGN(Promise<T>);
+};
+
 }  // namespace webrunner
 
 #endif  // WEBRUNNER_BROWSER_TEST_COMMON_H_