Add remoting and PPAPI tests to GN build

remoting/remoting_host.gypi

Index: remoting/remoting_host.gypi
diff --git a/remoting/remoting_host.gypi b/remoting/remoting_host.gypi
index e818a971bc6b93e2170f4d389d1d5def6a90f173..f780e52235c795d55ef653a7640c08b1d43d1027 100644
--- a/remoting/remoting_host.gypi
+++ b/remoting/remoting_host.gypi
@@ -211,6 +211,7 @@
         },  # end of target 'remoting_host'
 
         {
+          # GN version: //remoting/host/native_messaging
           'target_name': 'remoting_native_messaging_base',
           'type': 'static_library',
           'variables': { 'enable_wexit_time_destructors': 1, },
@@ -218,6 +219,7 @@
             '../base/base.gyp:base',
           ],
           'sources': [
+            # Note: sources list duplicated in GN build.
             'host/native_messaging/native_messaging_pipe.cc',
             'host/native_messaging/native_messaging_pipe.h',
             'host/native_messaging/native_messaging_reader.cc',
@@ -230,6 +232,7 @@
         },  # end of target 'remoting_native_messaging_base'
 
         {
+          # GN version: //remoting/host/setup
           'target_name': 'remoting_host_setup_base',
           'type': 'static_library',
           'variables': { 'enable_wexit_time_destructors': 1, },