Add a run-time switch for lacros-chrome-path.

Setting the switch will cause ash-chrome to launch the lacros-chrome
binary from the given path rather than from component updater.

Bug: 1077348
Change-Id: I50f5a1be84c31df434b37997007112e7c1296767
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2200078
Commit-Queue: Erik Chen <erikchen@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Auto-Submit: Erik Chen <erikchen@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#768532}

chrome/browser/chromeos/lacros/lacros_loader.cc

@@ -69,6 +69,17 @@ void LacrosLoader::Init() {
   if (chromeos::features::IsLacrosSupportEnabled()) {
     // TODO(crbug.com/1078607): Remove non-error logging from this class.
     LOG(WARNING) << "Starting lacros component load.";
+
+    // If the user has specified a path for the lacros-chrome binary, use that
+    // rather than component manager.
+    base::FilePath lacros_chrome_path =
+        base::CommandLine::ForCurrentProcess()->GetSwitchValuePath(
+            chromeos::switches::kLacrosChromePath);
+    if (!lacros_chrome_path.empty()) {
+      OnLoadComplete(CrOSComponentManager::Error::NONE, lacros_chrome_path);
+      return;
+    }
+
     cros_component_manager_->Load(kLacrosComponentName,
                                   CrOSComponentManager::MountPolicy::kMount,
                                   CrOSComponentManager::UpdatePolicy::kForce,

chromeos/constants/chromeos_switches.cc

@@ -396,6 +396,11 @@ const char kIgnoreUserProfileMappingForTests[] =
 // chrome://flags
 const char kKernelnextRestrictVMs[] = "kernelnext-restrict-vms";
 
+// If this switch is set, then ash-chrome will exec the lacros-chrome binary
+// from the indicated path rather than from component updater. Note that the
+// path should be to a directory that contains a binary named 'chrome'.
+const char kLacrosChromePath[] = "lacros-chrome-path";
+
 // Enables Chrome-as-a-login-manager behavior.
 const char kLoginManager[] = "login-manager";
 

chromeos/constants/chromeos_switches.h

@@ -161,6 +161,7 @@ COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kHomedir[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kIgnoreUserProfileMappingForTests[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kKernelnextRestrictVMs[];
+COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kLacrosChromePath[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kLoginManager[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kLoginProfile[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kLoginUser[];