[DevTools] Split auto-attach part of TargetHandler into a separate class

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 4fdcfe9ad6afdf85aabea924b5c28d3ddc8c909c..a49ab41dd2c731910004d35a82d5527cddb90979 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -557,6 +557,8 @@ source_set("browser") {
     "devtools/protocol/storage_handler.h",
     "devtools/protocol/system_info_handler.cc",
     "devtools/protocol/system_info_handler.h",
+    "devtools/protocol/target_auto_attacher.cc",
+    "devtools/protocol/target_auto_attacher.h",
     "devtools/protocol/target_handler.cc",
     "devtools/protocol/target_handler.h",
     "devtools/protocol/tethering_handler.cc",
@@ -1642,9 +1644,9 @@ source_set("browser") {
 
     deps += [
       "//jingle:jingle_glue",
-      "//third_party/webrtc/rtc_base:rtc_base",
       "//third_party/webrtc/media:rtc_media_base",
       "//third_party/webrtc/modules/desktop_capture:primitives",
+      "//third_party/webrtc/rtc_base:rtc_base",
       "//third_party/webrtc_overrides:init_webrtc",
     ]
   }