Replacing rtc::TimeDelta with webrtc::TimeDelta.

This removes the redundant type and replaces all usages. A slight change
in behavior is that we no longer get nanosecond resolution. This should
not matter since no current code requires nanosecond resolution.

Bug: webrtc:9155
Change-Id: I04334e08c686d95731621a6c8a7e40400d0ae3b2
Reviewed-on: https://webrtc-review.googlesource.com/71163
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23174}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index c3d0546..cb984e2 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -1028,7 +1028,6 @@
     "testechoserver.h",
     "testutils.cc",
     "testutils.h",
-    "timedelta.h",
     "virtualsocketserver.cc",
     "virtualsocketserver.h",
   ]
@@ -1038,6 +1037,7 @@
     ":checks",
     ":rtc_base",
     ":stringutils",
+    "../api/units:time_delta",
     "../test:field_trial",
     "../test:test_support",
     "system:fallthrough",