[DevTools] removed DevToolsAgentHost::kTypeExternal

This string is not used anywhere in Chromium codebase.

R=pfeldman@chromium.org

Bug: none
Change-Id: Id3b32083bc7090e66cd3d3930241bf7a2fe86bd7
Reviewed-on: https://chromium-review.googlesource.com/566565Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487553}

content/browser/devtools/devtools_agent_host_impl.cc

@@ -41,7 +41,6 @@ char DevToolsAgentHost::kTypePage[] = "page";
 char DevToolsAgentHost::kTypeFrame[] = "iframe";
 char DevToolsAgentHost::kTypeSharedWorker[] = "shared_worker";
 char DevToolsAgentHost::kTypeServiceWorker[] = "service_worker";
-char DevToolsAgentHost::kTypeExternal[] = "external";
 char DevToolsAgentHost::kTypeBrowser[] = "browser";
 char DevToolsAgentHost::kTypeGuest[] = "webview";
 char DevToolsAgentHost::kTypeOther[] = "other";

content/public/browser/devtools_agent_host.h

@@ -41,7 +41,6 @@ class CONTENT_EXPORT DevToolsAgentHost
   static char kTypeFrame[];
   static char kTypeSharedWorker[];
   static char kTypeServiceWorker[];
-  static char kTypeExternal[];
   static char kTypeBrowser[];
   static char kTypeGuest[];
   static char kTypeOther[];