Tightening visibility and removing a public_dep.

This CL aligns the visibility and the dependency between the _objc
and the _generic targets to the standard decided in:
https://codereview.webrtc.org/3001623003.

BUG=webrtc:7743
NOTRY=True

Review-Url: https://codereview.webrtc.org/3012753003
Cr-Original-Commit-Position: refs/heads/master@{#19668}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: edb8429ba3df2f359813498e63bc269fe495f3f1
diff --git a/modules/desktop_capture/BUILD.gn b/modules/desktop_capture/BUILD.gn
index 2f8f8bf..6b7fb22 100644
--- a/modules/desktop_capture/BUILD.gn
+++ b/modules/desktop_capture/BUILD.gn
@@ -166,30 +166,25 @@
 }
 
 rtc_source_set("desktop_capture") {
+  public_deps = [
+    ":desktop_capture_generic",
+  ]
   if (is_mac) {
-    public_deps = [
-      ":desktop_capture_objc",
-    ]
-  } else {
-    public_deps = [
-      ":desktop_capture_generic",
-    ]
+    public_deps += [ ":desktop_capture_objc" ]
   }
 }
 
 if (is_mac) {
   rtc_source_set("desktop_capture_objc") {
-    visibility = [ ":*" ]
+    visibility = [ ":desktop_capture" ]
     sources = [
       "mac/desktop_configuration.mm",
       "mouse_cursor_monitor_mac.mm",
       "screen_capturer_mac.mm",
       "window_capturer_mac.mm",
     ]
-    public_deps = [
-      ":desktop_capture_generic",
-    ]
     deps = [
+      ":desktop_capture_generic",
       ":primitives",
       "../../rtc_base:rtc_base",
       "../../rtc_base:rtc_base_approved",
@@ -203,7 +198,10 @@
 }
 
 rtc_static_library("desktop_capture_generic") {
-  visibility = [ ":*" ]
+  visibility = [
+    ":desktop_capture",
+    ":desktop_capture_objc",
+  ]
   sources = [
     "blank_detector_desktop_capturer_wrapper.cc",
     "blank_detector_desktop_capturer_wrapper.h",