[Telemetry SWX] Add telemetry-extension-dir switch name

Add telemetry-extension-dir command line switch name to be able to load
the Telemetry System Web Extension from disk.

Bug: b:156583406
Test: Not needed. chrome build is green

Change-Id: Id8ae2a8c6a27fa0637264ac9e6e14467e66e8de1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2257235
Commit-Queue: Mahmoud Gawad <mgawad@google.com>
Reviewed-by: Oleh Lamzin <lamzin@google.com>
Cr-Commit-Position: refs/heads/master@{#781358}

chromeos/constants/chromeos_switches.cc

@@ -520,6 +520,9 @@ const char kShowOobeDevOverlay[] = "show-oobe-dev-overlay";
 // Specifies directory for screenshots taken with OOBE UI Debugger.
 const char kOobeScreenshotDirectory[] = "oobe-screenshot-dir";
 
+// Specifies directory for the Telemetry System Web Extension.
+const char kTelemetryExtensionDirectory[] = "telemetry-extension-dir";
+
 // Enables testing for encryption migration UI.
 const char kTestEncryptionMigrationUI[] = "test-encryption-migration-ui";
 

chromeos/constants/chromeos_switches.h

@@ -204,6 +204,8 @@ COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kShowOobeDevOverlay[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kOobeScreenshotDirectory[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
+extern const char kTelemetryExtensionDirectory[];
+COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kTestEncryptionMigrationUI[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kTestWallpaperServer[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kTetherStub[];