Split GCMDriver into platform-specific implementations

components/gcm_driver.gypi

Index: components/gcm_driver.gypi
diff --git a/components/gcm_driver.gypi b/components/gcm_driver.gypi
index a2e545568bc81b8bd6916abd92ef9f0086706325..7b3bb4a2ab00b5e86024f66bdd1bf70e6710be55 100644
--- a/components/gcm_driver.gypi
+++ b/components/gcm_driver.gypi
@@ -28,6 +28,8 @@
         'gcm_driver/gcm_driver.h',
         'gcm_driver/gcm_driver_android.cc',
         'gcm_driver/gcm_driver_android.h',
+        'gcm_driver/gcm_driver_desktop.cc',
+        'gcm_driver/gcm_driver_desktop.h',
         'gcm_driver/system_encryptor.cc',
         'gcm_driver/system_encryptor.h',
       ],
@@ -36,6 +38,10 @@
           'dependencies': [
             'gcm_driver_jni_headers',
           ],
+          'sources!': [
+            'gcm_driver/gcm_driver_desktop.cc',
+            'gcm_driver/gcm_driver_desktop.h',
+          ],
         }],
       ],
     },
@@ -57,6 +63,8 @@
         'gcm_driver/fake_gcm_client.h',
         'gcm_driver/fake_gcm_client_factory.cc',
         'gcm_driver/fake_gcm_client_factory.h',
+        'gcm_driver/fake_gcm_driver.cc',
+        'gcm_driver/fake_gcm_driver.h',
       ],
     },    
   ],