Remove race condition in Smb Share discovery

Stores a mount call if host discovery is not yet complete and runs it as
soon as the first share names start coming back, indicating that host
discovery is complete.

The mount can be attempted before share discovery is complete because
mounting via a hostname is only dependent on host discovery for name
resolution.

Bug: 757625, 863178
Change-Id: If53ec9061c79a4f408278be4ddd990a7c9ca3791
Reviewed-on: https://chromium-review.googlesource.com/1136528Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575477}

chrome/browser/ui/webui/settings/chromeos/smb_handler.cc

@@ -59,9 +59,17 @@ void SmbHandler::HandleSmbMount(const base::ListValue* args) {
   mo.display_name = mount_name.empty() ? mount_url : mount_name;
   mo.writable = true;
 
-  service->Mount(mo, base::FilePath(mount_url), username, password,
-                 base::BindOnce(&SmbHandler::HandleSmbMountResponse,
-                                weak_ptr_factory_.GetWeakPtr()));
+  auto mount_response = base::BindOnce(&SmbHandler::HandleSmbMountResponse,
+                                       weak_ptr_factory_.GetWeakPtr());
+  auto mount_call = base::BindOnce(
+      &smb_client::SmbService::Mount, base::Unretained(service), mo,
+      base::FilePath(mount_url), username, password, std::move(mount_response));
+
+  if (host_discovery_done_) {
+    std::move(mount_call).Run();
+  } else {
+    stored_mount_call_ = std::move(mount_call);
+  }
 }
 
 void SmbHandler::HandleSmbMountResponse(SmbMountResult result) {
@@ -78,6 +86,11 @@ void SmbHandler::HandleStartDiscovery(const base::ListValue* args) {
 
 void SmbHandler::HandleGatherSharesResponse(
     const std::vector<smb_client::SmbUrl>& shares_gathered) {
+  host_discovery_done_ = true;
+  if (!stored_mount_call_.is_null()) {
+    std::move(stored_mount_call_).Run();
+  }
+
   // TODO(zentaro): Pass the shares discovered back to the UI.
   // https://crbug.com/852199.
 }

chrome/browser/ui/webui/settings/chromeos/smb_handler.h

@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_SMB_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_SMB_HANDLER_H_
 
+#include "base/callback_forward.h"
 #include "base/files/file.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ -41,6 +42,8 @@ class SmbHandler : public ::settings::SettingsPageUIHandler {
   void HandleGatherSharesResponse(
       const std::vector<smb_client::SmbUrl>& shares_gathered);
 
+  bool host_discovery_done_ = false;
+  base::OnceClosure stored_mount_call_;
   Profile* const profile_;
   base::WeakPtrFactory<SmbHandler> weak_ptr_factory_;