scanning: Pass capabilities by const reference

Since there's no benefit of passing lorgnette::ScannerCapabilities by
value (e.g. copy elision), pass it by const reference.

Bug: None
Change-Id: Ia9457c83c6aafbf7a52e32bfc1d350100d8e64fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2424743Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809804}

chrome/browser/chromeos/scanning/lorgnette_scanner_manager.h

@@ -26,7 +26,7 @@ class LorgnetteScannerManager : public KeyedService {
   using GetScannerNamesCallback =
       base::OnceCallback<void(std::vector<std::string> scanner_names)>;
   using GetScannerCapabilitiesCallback = base::OnceCallback<void(
-      base::Optional<lorgnette::ScannerCapabilities> capabilities)>;
+      const base::Optional<lorgnette::ScannerCapabilities>& capabilities)>;
   using PageCallback = base::RepeatingCallback<void(std::string scan_data)>;
   using ScanCallback = base::OnceCallback<void(bool success)>;
 

chrome/browser/chromeos/scanning/lorgnette_scanner_manager_unittest.cc

@@ -202,7 +202,8 @@ class LorgnetteScannerManagerTest : public testing::Test {
   }
 
   void GetScannerCapabilitiesCallback(
-      base::Optional<lorgnette::ScannerCapabilities> scanner_capabilities) {
+      const base::Optional<lorgnette::ScannerCapabilities>&
+          scanner_capabilities) {
     scanner_capabilities_ = scanner_capabilities;
     run_loop_->Quit();
   }

chrome/browser/chromeos/scanning/scan_service.cc

@@ -78,7 +78,7 @@ void ScanService::OnScannerNamesReceived(
 
 void ScanService::OnScannerCapabilitiesReceived(
     GetScannerCapabilitiesCallback callback,
-    base::Optional<lorgnette::ScannerCapabilities> capabilities) {
+    const base::Optional<lorgnette::ScannerCapabilities>& capabilities) {
   if (!capabilities) {
     LOG(ERROR) << "Failed to get scanner capabilities.";
     std::move(callback).Run(mojo_ipc::ScannerCapabilities::New());

chrome/browser/chromeos/scanning/scan_service.h

@@ -54,7 +54,7 @@ class ScanService : public scanning::mojom::ScanService, public KeyedService {
   // LorgnetteScannerManager::GetScannerCapabilities().
   void OnScannerCapabilitiesReceived(
       GetScannerCapabilitiesCallback callback,
-      base::Optional<lorgnette::ScannerCapabilities> capabilities);
+      const base::Optional<lorgnette::ScannerCapabilities>& capabilities);
 
   // Map of scanner IDs to display names. Used to pass the correct display name
   // to LorgnetteScannerManager when clients provide an ID.