Added gyp variable to include/exclude all tests.

BUG=
TEST=

Review URL: https://webrtc-codereview.appspot.com/597004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@2292 4adac7df-926f-26a2-2b94-8c16560cd09d

src/common_audio/signal_processing/signal_processing.gypi

@@ -59,7 +59,7 @@
     }, # spl
   ], # targets
   'conditions': [
-    ['build_with_chromium==0', {
+    ['include_tests==1', {
       'targets': [
         {
           'target_name': 'signal_processing_unittests',
@@ -74,7 +74,7 @@
           ],
         }, # spl_unittests
       ], # targets
-    }], # build_with_chromium
+    }], # include_tests
   ], # conditions
 }