videoadapter_unittest.cc: Revert removal of '#if defined(HAVE_WEBRTC_VIDEO)'

This CL reverts some parts of "Delete VideoAdapter::AdaptFrame" https://webrtc-codereview.appspot.com/44769004/.

Reason for revert: Should not touch HAVE_WEBRTC_VIDEO since libjingle_media_unittests does not compile without anyway.

BUG=4317
R=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48699005

Cr-Commit-Position: refs/heads/master@{#8888}

talk/media/base/videoadapter_unittest.cc

@@ -25,6 +25,8 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+// If we don't have a WebRtcVideoFrame, just skip all of these tests.
+#if defined(HAVE_WEBRTC_VIDEO)
 #include <limits.h>  // For INT_MAX
 #include <string>
 #include <vector>
@@ -1303,3 +1305,4 @@ TEST_F(VideoAdapterTest, CpuIgnoresSpikes) {
 }
 
 }  // namespace cricket
+#endif  // HAVE_WEBRTC_VIDEO