Add missing BUILD.gn dependencies and enable GN checks.

Adds some missing dependencies in //third_party/webrtc_overrides, and
enables GN checks on that directory.

Bug: 812058
Change-Id: I23fc0f45887a2c9ab50c6d217c9fb2c327ec4e7e
Reviewed-on: https://chromium-review.googlesource.com/974755
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545101}

.gn

@@ -161,6 +161,8 @@ check_targets = [
   "//third_party/snappy/*",
 
   #"//third_party/WebKit/*",  # Errors: https://crbug.com/800764
+  #"//third_party/webrtc/*",
+  "//third_party/webrtc_overrides/*",
   "//tools/*",
 
   "//ui/*",

third_party/webrtc_overrides/BUILD.gn

@@ -82,6 +82,10 @@ static_library("webrtc") {
       "field_trial.cc",
       "runtime_enabled_features.cc",
     ]
+    deps += [
+      "//base",
+      "//third_party/webrtc/system_wrappers:runtime_enabled_features_api",
+    ]
   }
 
   configs += [
@@ -112,6 +116,9 @@ static_library("init_webrtc") {
   ]
   deps = [
     ":task_queue_impl",
+    "//base",
+    "//third_party/webrtc/rtc_base",
+    "//third_party/webrtc/system_wrappers",
   ]
 }
 
@@ -144,6 +151,7 @@ source_set("task_queue_impl") {
   ]
   deps = [
     "//base",
+    "//third_party/webrtc/rtc_base:refcount",
     "//third_party/webrtc/rtc_base:rtc_task_queue_api",
   ]
 }