Roll third_party/inspector_protocol to 4d389ba

This roll includes:
  - [inspector_protocol] first class citizien .pdl support

+ migrated cros_protocol.json to .pdl

TBR=dgozman@chromium.org,dpranke@chromium.org,pfeldman@chromium.org
NOPRESUBMIT=true
Bug:none

Change-Id: I0fff1582bd41115e2aa348008c7a5d48f5c59a7e
Reviewed-on: https://chromium-review.googlesource.com/1014468
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#551382}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a42a629f67ac9aae0aaa8fbd912c654559c5d880
diff --git a/scripts/compile_frontend.py b/scripts/compile_frontend.py
index 1c45aa0..223b014 100755
--- a/scripts/compile_frontend.py
+++ b/scripts/compile_frontend.py
@@ -334,8 +334,8 @@
         protocol_externs_file = args.protocol_externs_file
     else:
         generate_protocol_externs.generate_protocol_externs(protocol_externs_file,
-                                                            path.join(inspector_path, 'browser_protocol.json'),
-                                                            path.join(v8_inspector_path, 'js_protocol.json'))
+                                                            path.join(inspector_path, 'browser_protocol.pdl'),
+                                                            path.join(v8_inspector_path, 'js_protocol.pdl'))
     loader = modular_build.DescriptorLoader(devtools_frontend_path)
     descriptors = loader.load_applications(application_descriptors)
     modules_by_name = descriptors.modules