Create function in Print Preview to check for mounted Drive

This function will be used to determine if the Chrome OS user should see
the Save to Drive option in their Print Preview dropdown.

Reasons why Drive could not be mounted (function would return false)
include: Drive is disabled by the user, disabled by enterprise policy,
or is in a crashing state.

Bug: 1112416
Change-Id: Ibfc1cbf7c0662bd6eb15fb9204ef5b8c9812097e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339919
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795637}

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

@@ -79,6 +79,7 @@
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/account_manager/account_manager_util.h"
+#include "chrome/browser/chromeos/drive/drive_integration_service.h"
 #include "chrome/browser/device_identity/device_oauth2_token_service.h"
 #include "chrome/browser/device_identity/device_oauth2_token_service_factory.h"
 #include "chrome/browser/ui/settings_window_manager_chromeos.h"
@@ -442,6 +443,10 @@ void PrintPreviewHandler::RegisterMessages() {
       base::BindRepeating(
           &PrintPreviewHandler::HandleRequestPrinterStatusUpdate,
           base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      "isDriveMounted",
+      base::BindRepeating(&PrintPreviewHandler::HandleIsDriveMounted,
+                          base::Unretained(this)));
 #endif
 }
 
@@ -1400,6 +1405,18 @@ void PrintPreviewHandler::OnPrinterStatusUpdated(
     const base::Value& cups_printer_status) {
   ResolveJavascriptCallback(base::Value(callback_id), cups_printer_status);
 }
+
+void PrintPreviewHandler::HandleIsDriveMounted(const base::ListValue* args) {
+  CHECK_EQ(1U, args->GetSize());
+  const std::string& callback_id = args->GetList()[0].GetString();
+
+  drive::DriveIntegrationService* drive_service =
+      drive::DriveIntegrationServiceFactory::GetForProfile(
+          Profile::FromWebUI(web_ui()));
+  ResolveJavascriptCallback(
+      base::Value(callback_id),
+      base::Value(drive_service && drive_service->IsMounted()));
+}
 #endif
 
 }  // namespace printing

chrome/browser/ui/webui/print_preview/print_preview_handler.h

@@ -318,6 +318,10 @@ class PrintPreviewHandler : public content::WebUIMessageHandler,
   // Resolves callback with printer status.
   void OnPrinterStatusUpdated(const std::string& callback_id,
                               const base::Value& cups_printer_status);
+
+  // Resolves Javascript callback with true if the user's local Drive folder is
+  // mounted.
+  void HandleIsDriveMounted(const base::ListValue* args);
 #endif
 
   // A count of how many requests received to regenerate preview data.