[Fuchsia] Fix OzonePlatformScenic handling of MessageLoop destruction.

Tear down all sub-components of the OzonePlatformScenic implementation
on MessageLoop destruction, to prevent components which set FIDL error-
handlers from observing ZX_ERR_CANCELED events.

MessagePumpFuchsia is also updated to print out the base::Location at
which the {ZxHandle|Fd}WatchController was created, to help in
diagnosing issues with failing asynchronous watch operations.

Bug: 927400
Change-Id: I91ad15b5a5f83c9e45b602a0647745813c55aef9
Reviewed-on: https://chromium-review.googlesource.com/c/1490953Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636197}

base/message_loop/message_pump_fuchsia.cc

@@ -34,7 +34,8 @@ bool MessagePumpFuchsia::ZxHandleWatchController::WaitBegin() {
   zx_status_t status =
       async_begin_wait(weak_pump_->async_loop_->dispatcher(), this);
   if (status != ZX_OK) {
-    ZX_DLOG(ERROR, status) << "async_begin_wait() failed";
+    ZX_DLOG(ERROR, status) << "async_begin_wait():"
+                           << created_from_location_.ToString();
     async_wait_t::handler = nullptr;
     return false;
   }
@@ -66,7 +67,8 @@ bool MessagePumpFuchsia::ZxHandleWatchController::StopWatchingZxHandle() {
 
   zx_status_t result =
       async_cancel_wait(weak_pump_->async_loop_->dispatcher(), this);
-  ZX_DLOG_IF(ERROR, result != ZX_OK, result) << "async_cancel_wait failed";
+  ZX_DLOG_IF(ERROR, result != ZX_OK, result)
+      << "async_cancel_wait(): " << created_from_location_.ToString();
   return result == ZX_OK;
 }
 
@@ -78,14 +80,16 @@ void MessagePumpFuchsia::ZxHandleWatchController::HandleSignal(
     const zx_packet_signal_t* signal) {
   TRACE_EVENT0("toplevel", "ZxHandleSignal");
 
+  ZxHandleWatchController* controller =
+      static_cast<ZxHandleWatchController*>(wait);
+  DCHECK_EQ(controller->handler, &HandleSignal);
+
   if (status != ZX_OK) {
-    ZX_LOG(WARNING, status) << "async wait failed";
+    ZX_DLOG(WARNING, status) << "async wait failed: "
+                             << controller->created_from_location_.ToString();
     return;
   }
 
-  ZxHandleWatchController* controller =
-      static_cast<ZxHandleWatchController*>(wait);
-  DCHECK_EQ(controller->handler, &HandleSignal);
   controller->handler = nullptr;
 
   // |signal| can include other spurious things, in particular, that an fd
@@ -150,7 +154,8 @@ bool MessagePumpFuchsia::FdWatchController::WaitBegin() {
   // their current state, so we must do this every time we begin to wait.
   fdio_unsafe_wait_begin(io_, desired_events_, &object, &trigger);
   if (async_wait_t::object == ZX_HANDLE_INVALID) {
-    DLOG(ERROR) << "fdio_wait_begin failed";
+    DLOG(ERROR) << "fdio_wait_begin failed: "
+                << ZxHandleWatchController::created_from_location_.ToString();
     return false;
   }
 

ui/ozone/platform/scenic/ozone_platform_scenic.cc

@@ -154,11 +154,19 @@ class OzonePlatformScenic
   }
 
  private:
-  // Performs graceful cleanup tasks on main message loop teardown.
-  void Shutdown() { window_manager_.reset(); }
-
   // base::MessageLoopCurrent::DestructionObserver implementation.
-  void WillDestroyCurrentMessageLoop() override { Shutdown(); }
+  void WillDestroyCurrentMessageLoop() override {
+    // We must ensure to destroy any resources which rely on the MessageLoop's
+    // async_dispatcher.
+    scenic_gpu_host_ptr_ = nullptr;
+    surface_factory_ = nullptr;
+    scenic_gpu_host_ = nullptr;
+    overlay_manager_ = nullptr;
+    input_controller_ = nullptr;
+    cursor_factory_ozone_ = nullptr;
+    platform_event_source_ = nullptr;
+    window_manager_ = nullptr;
+  }
 
   std::unique_ptr<ScenicWindowManager> window_manager_;