Rename EncodingEnum namepsace to encoding_enum

https://google.github.io/styleguide/cppguide.html#Namespace_Names
> Namespace names are all lower-case.

This CL has no behavior changes.

Bug: 889726
Change-Id: Icb9edd7ce1fddb023b92e27e289c27aa88c88473
Reviewed-on: https://chromium-review.googlesource.com/c/1351203Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: DongJun Kim <djmix.kim@samsung.com>
Cr-Commit-Position: refs/heads/master@{#611514}

third_party/blink/renderer/core/inspector/inspector_audits_agent.cc

@@ -16,7 +16,7 @@ namespace blink {
 using protocol::Maybe;
 using protocol::Response;
 
-namespace EncodingEnum = protocol::Audits::GetEncodedResponse::EncodingEnum;
+namespace encoding_enum = protocol::Audits::GetEncodedResponse::EncodingEnum;
 
 namespace {
 
@@ -82,8 +82,8 @@ protocol::Response InspectorAuditsAgent::getEncodedResponse(
     Maybe<protocol::Binary>* out_body,
     int* out_original_size,
     int* out_encoded_size) {
-  DCHECK(encoding == EncodingEnum::Jpeg || encoding == EncodingEnum::Png ||
-         encoding == EncodingEnum::Webp);
+  DCHECK(encoding == encoding_enum::Jpeg || encoding == encoding_enum::Png ||
+         encoding == encoding_enum::Webp);
 
   String body;
   bool is_base64_encoded;

third_party/blink/tools/blinkpy/presubmit/audit_non_blink_usage.py

@@ -231,6 +231,7 @@ _CONFIG = [
             'css_parsing_utils::.+',
             'cssvalue::.+',
             'encoding::.+',
+            'encoding_enum::.+',
             'event_handling_util::.+',
             'event_util::.+',
             'file_error::.+',