Remove old webrtc/base directory

The content of webrtc/base has been moved to webrtc/rtc_base and we can
now remove the original directory.

BUG=webrtc:7634

Review-Url: https://codereview.webrtc.org/2994743002
Cr-Commit-Position: refs/heads/master@{#19361}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 497e182..9a76412 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -508,26 +508,6 @@
   return []
 
 
-def _CheckNoChangesToWebRTCBase(input_api, output_api):
-  """Checks that no changes refer to webrtc/base."""
-  problems = []
-
-  for f in input_api.AffectedFiles():
-    if os.path.join('webrtc', 'base') in f.LocalPath():
-      problems.append('    ' + f.LocalPath())
-      continue
-    for line_num, line in f.ChangedContents():
-      if 'webrtc/base' in line:
-        problems.append('    %s: %s' % (f.LocalPath(), line_num))
-
-  if problems:
-    return [output_api.PresubmitPromptWarning(
-        'webrtc/base is being moved to webrtc/rtc_base (See '
-        'bugs.webrtc.org/7634). Please refer to webrtc/rtc_base instead in the '
-        'following files:\n' + '\n'.join(problems))]
-  return []
-
-
 def _CommonChecks(input_api, output_api):
   """Checks common to both upload and commit."""
   results = []
@@ -596,7 +576,6 @@
   results.extend(_CheckUsageOfGoogleProtobufNamespace(input_api, output_api))
   results.extend(_CheckOrphanHeaders(input_api, output_api))
   results.extend(_CheckNewLineAtTheEndOfProtoFiles(input_api, output_api))
-  results.extend(_CheckNoChangesToWebRTCBase(input_api, output_api))
   return results
 
 
diff --git a/webrtc/base/README.md b/webrtc/base/README.md
deleted file mode 100644
index 3d0bf66..0000000
--- a/webrtc/base/README.md
+++ /dev/null
@@ -1,20 +0,0 @@
-# What?
-
-The contents of base have moved to rtc_base.
-
-# Why?
-
-We want to move all the contents in the webrtc directory to top-level, because:
-* When we migrate from Rietveld to PolyGerrit we won't be able to apply WebRTC
-patches on Chromium trybots (which is a very useful feature, especially as we
-plan to have such trybots in our default trybot set).
-This is because PolyGerrit needs the repo in Chromium to be the same as the
-WebRTC repo, otherwise it won’t be able to apply the patch.
-* To fully automate rolling into Chromium DEPS, we wish to use the LKGR finder,
-but doing so is blocked on this (needs the same revision hashes to avoid ugly
-hacks). See [this bug](http://crbug.com/666726).
-
-# Tracking Bugs
-
-[Chromium tracking bug](http://crbug.com/611808)
-[WebRTC tracking bug](https://bugs.chromium.org/p/webrtc/issues/detail?id=7634)