Add a default delegate time scale converter (#5076)

Summary:
Pull Request resolved: #5076

By default, the non-delegated events have a time scale converter, but delegated events do not, and this has caused confusion for users: [post](https://fb.workplace.com/groups/pytorch.edge.users/permalink/1562687731268181/), [Issue #4504](#4504).

This diff gives a quick solution for the problem to unblock ET Beta. The rationale is that since for non-delegated ops, we have the default time scale:
```
source_time_scale: TimeScale = TimeScale.NS,
target_time_scale: TimeScale = TimeScale.MS,
```
And the conversion rate is 10^6 (because 1 MS = 10^6 NS), so it makes sense to set a default converter function for delegated ops to be `input_time/(1000 * 1000)` as well. Similar converter functions have been used by [coreml](https://www.internalfb.com/code/fbsource/[76be64aab17c]/fbcode/executorch/examples/apple/coreml/scripts/inspector_utils.py?lines=259-262) and [vulkan](https://fburl.com/code/5cu6fx2b) already.

The proper solution to write the convertion in etdump is tracked by T198369344 and T198369419

Differential Revision: D62160650

Author: Olivia-liu

devtools/inspector/_inspector.py

@@ -40,6 +40,7 @@
 from executorch.devtools.etrecord import ETRecord, parse_etrecord
 from executorch.devtools.inspector._inspector_utils import (
     create_debug_handle_to_op_node_mapping,
+    default_delegate_time_scale_converter,
     EDGE_DIALECT_GRAPH_KEY,
     EXCLUDED_COLUMNS_WHEN_PRINTING,
     EXCLUDED_EVENTS_WHEN_PRINTING,
@@ -949,9 +950,9 @@ def __init__(
         delegate_metadata_parser: Optional[
             Callable[[List[str]], Dict[str, Any]]
         ] = None,
-        delegate_time_scale_converter: Optional[
-            Callable[[Union[int, str], Union[int, float]], Union[int, float]]
-        ] = None,
+        delegate_time_scale_converter: Callable[
+            [Union[int, str], Union[int, float]], Union[int, float]
+        ] = default_delegate_time_scale_converter,
         enable_module_hierarchy: bool = False,
     ) -> None:
         r"""
@@ -966,6 +967,8 @@ def __init__(
             debug_buffer_path: Debug buffer file path that contains the debug data referenced by ETDump for intermediate and program outputs.
             delegate_metadata_parser: Optional function to parse delegate metadata from an Profiling Event. Expected signature of the function is:
                     (delegate_metadata_list: List[bytes]) -> Union[List[str], Dict[str, Any]]
+            delegate_time_scale_converter: The function to convert the time scale of delegate profiling data. Default to dividing by 10^6.
+            enable_module_hierarchy: Enable submodules in the operator graph. Defaults to False.
 
         Returns:
             None

devtools/inspector/_inspector_utils.py

@@ -429,3 +429,17 @@ def compare_results(
                 print("\n")
 
     return results
+
+
+def default_delegate_time_scale_converter(
+    event_name: Union[str, int], input_time: Union[int, float]
+) -> Union[int, float]:
+    """
+    Default time scale converter for delegate events. This function divides the input time by 10^6.
+    Args:
+        event_name (Union[str, int]): The name of the event. Notice that this is intentionally ignored in this function.
+        input_time (Union[int, float]): The raw input time.
+    Returns:
+        Union[int, float]: The converted time.
+    """
+    return input_time / (1000 * 1000)

devtools/inspector/tests/inspector_utils_test.py

@@ -24,6 +24,7 @@
 from executorch.devtools.etrecord.tests.etrecord_test import TestETRecord
 from executorch.devtools.inspector._inspector_utils import (
     create_debug_handle_to_op_node_mapping,
+    default_delegate_time_scale_converter,
     EDGE_DIALECT_GRAPH_KEY,
     find_populated_event,
     gen_graphs_from_etrecord,
@@ -170,6 +171,9 @@ def test_is_inference_output_equal_returns_true_for_same_strs(self):
             )
         )
 
+    def test_default_delegate_time_scale_converter(self):
+        self.assertEqual(default_delegate_time_scale_converter("op_name", 10000000), 10)
+
 
 def gen_mock_operator_graph_with_expected_map() -> (
     Tuple[OperatorGraph, Dict[int, OperatorNode]]