Remove remains of webrtc/base

All downstream code have been updated to the new location.

In PRESUBMIT.py:
* Remove webrtc/rtc_base from CPP_BLACKLIST
* Add webrtc/rtc_base to LEGACY_API_DIRS

Fix some duplicated paths in
webrtc/modules/audio_processing/test/conversational_speech/BUILD.gn

BUG=webrtc:7634
TBR=kwiberg@webrtc.org

Review-Url: https://codereview.webrtc.org/2976293002
Cr-Commit-Position: refs/heads/master@{#19094}
diff --git a/webrtc/p2p/BUILD.gn b/webrtc/p2p/BUILD.gn
index daa2d84..16b8762 100644
--- a/webrtc/p2p/BUILD.gn
+++ b/webrtc/p2p/BUILD.gn
@@ -87,7 +87,7 @@
   deps = [
     "../api:libjingle_peerconnection_api",
     "../api:ortc_api",
-    "../base:rtc_base",
+    "../rtc_base:rtc_base",
     "../system_wrappers:field_trial_api",
   ]
 
@@ -155,9 +155,9 @@
     deps = [
       ":rtc_p2p",
       "../api:ortc_api",
-      "../base:rtc_base",
-      "../base:rtc_base_approved",
-      "../base:rtc_base_tests_utils",
+      "../rtc_base:rtc_base",
+      "../rtc_base:rtc_base_approved",
+      "../rtc_base:rtc_base_tests_utils",
       "../test:test_support",
       "//testing/gmock",
     ]
@@ -209,9 +209,9 @@
       ":rtc_p2p",
       "../api:fakemetricsobserver",
       "../api:ortc_api",
-      "../base:rtc_base",
-      "../base:rtc_base_approved",
-      "../base:rtc_base_tests_utils",
+      "../rtc_base:rtc_base",
+      "../rtc_base:rtc_base_approved",
+      "../rtc_base:rtc_base_tests_utils",
       "../test:test_support",
       "//testing/gmock",
       "//testing/gtest",
@@ -238,7 +238,7 @@
   deps = [
     ":rtc_p2p",
     "..:webrtc_common",
-    "../base:rtc_base",
+    "../rtc_base:rtc_base",
   ]
 }
 
@@ -259,8 +259,8 @@
       ":libstunprober",
       ":p2p_test_utils",
       ":rtc_p2p",
-      "../base:rtc_base",
-      "../base:rtc_base_tests_utils",
+      "../rtc_base:rtc_base",
+      "../rtc_base:rtc_base_tests_utils",
       "//testing/gmock",
       "//testing/gtest",
     ]