After CL:1345374 metrics.ImportEvents are unused: remove

 - remove metrics.ImportEvents
 - remove metrics.timing.Variables.HISTORY_LOAD

No change in behavior, no new tests.

Bug: 905934, 847729
Change-Id: I2f5ab9659dc5e134bdb47d8c770a1f918b4a0126
Reviewed-on: https://chromium-review.googlesource.com/c/1345381Reviewed-by: Stuart Langley <slangley@chromium.org>
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610025}

ui/file_manager/file_manager/common/js/metrics_events.js

@@ -131,12 +131,6 @@ metrics.Management = {
       .dimension(metrics.Dimensions.CONSUMER_TYPE_MANAGER)
 };
 
-/** @enum {!analytics.EventBuilder} */
-metrics.ImportEvents = {
-  HISTORY_LOADED: metrics.event.Builders_.IMPORT
-      .action('History Loaded'),
-};
-
 /** @enum {!analytics.EventBuilder} */
 metrics.Internals = {
   UNRECOGNIZED_FILE_SYSTEM_PROVIDER: metrics.event.Builders_.INTERNALS
@@ -150,6 +144,5 @@ metrics.timing = metrics.timing || {};
 metrics.timing.Variables = {
   COMPUTE_HASH: 'Compute Content Hash',
   SEARCH_BY_HASH: 'Search By Hash',
-  HISTORY_LOAD: 'History Load',
   EXTRACT_THUMBNAIL_FROM_RAW: 'Extract Thumbnail From RAW'
 };