Wrap the p2p transport API in a compile time flag.

ppapi/ppapi_tests.gypi

Index: ppapi/ppapi_tests.gypi
diff --git a/ppapi/ppapi_tests.gypi b/ppapi/ppapi_tests.gypi
index 4c4271c8572ac602a418fe801c8f77812bcffdf9..0013e446c4fa328cf7a84e1391b527fe1b9e25cc 100644
--- a/ppapi/ppapi_tests.gypi
+++ b/ppapi/ppapi_tests.gypi
@@ -224,8 +224,6 @@
         'tests/test_scrollbar.cc',
         'tests/test_scrollbar.h',
         'tests/test_struct_sizes.c',
-        'tests/test_transport.cc',
-        'tests/test_transport.h',
         'tests/test_url_loader.cc',
         'tests/test_url_loader.h',
         'tests/test_url_util.cc',
@@ -258,6 +256,12 @@
           'product_name': 'ppapi_tests',
           'product_extension': 'plugin',
         }],
+        ['ppapi_transport==1', {
+          'sources': [
+            'tests/test_transport.cc',
+            'tests/test_transport.h',
+          ],
+        }],
       ],
 # TODO(dmichael):  Figure out what is wrong with the script on Windows and add
 #                  it as an automated action.