Support for TakeScreenshot in cros_platform.

telemetry/telemetry/internal/platform/cros_platform_backend.py

Index: telemetry/telemetry/internal/platform/cros_platform_backend.py
diff --git a/telemetry/telemetry/internal/platform/cros_platform_backend.py b/telemetry/telemetry/internal/platform/cros_platform_backend.py
index 08f03c2d2066ed5b8a0055b4003e6ece640859c3..bc87ab4c26ccaa6f0990aaddeeb21ba0f13360c0 100644
--- a/telemetry/telemetry/internal/platform/cros_platform_backend.py
+++ b/telemetry/telemetry/internal/platform/cros_platform_backend.py
@@ -167,3 +167,9 @@ class CrosPlatformBackend(
       logging.warning(
           'PathExists: params timeout and retries are not support on CrOS.')
     return self._cri.FileExistsOnDevice(path)
+
+  def CanTakeScreenshot(self):
+    return True
+
+  def TakeScreenshot(self, file_path):
+    return self._cri.TakeScreenshot(file_path)