[DevTools] Explicitly add Tethering domain to browser protocol.

chrome/browser/devtools/BUILD.gn

Index: chrome/browser/devtools/BUILD.gn
diff --git a/chrome/browser/devtools/BUILD.gn b/chrome/browser/devtools/BUILD.gn
index 7565b9e8b5c1d5bc4599b33d0821cbd1548fbf08..dce1eaa4e1452e2c50c3be81cb9cd71151da1fb9 100644
--- a/chrome/browser/devtools/BUILD.gn
+++ b/chrome/browser/devtools/BUILD.gn
@@ -6,7 +6,8 @@ action("devtools_protocol_constants") {
   script = "//content/public/browser/devtools_protocol_constants_generator.py"
 
   blink_protocol = "//third_party/WebKit/Source/devtools/protocol.json"
-  inputs = [ blink_protocol ]
+  browser_protocol = "//content/browser/devtools/browser_protocol.json"
+  inputs = [ blink_protocol, browser_protocol ]
   outputs = [
     "$target_gen_dir/devtools_protocol_constants.cc",
     "$target_gen_dir/devtools_protocol_constants.h",
@@ -15,6 +16,7 @@ action("devtools_protocol_constants") {
   args = [ "chrome" ]
   args += rebase_path(outputs, root_build_dir)
   args += [ rebase_path(blink_protocol, root_build_dir) ]
+  args += [ rebase_path(browser_protocol, root_build_dir) ]
 }
 
 # GYP version: chrome/chrome_debugger.gypi:debugger