Add macros and APIs for webrtc histograms.

BUG=crbug/419657

Code that links system_wrappers.gyp:system_wrappers should either:
- provide implementations for the APIs, or
- link with default implementations in system_wrappers.gyp:system_wrappers_default.

R=andresp@webrtc.org, kjellander@webrtc.org, mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/22809004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7508 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/webrtc_examples.gyp b/webrtc/webrtc_examples.gyp
index 0c7293f..4d63110 100644
--- a/webrtc/webrtc_examples.gyp
+++ b/webrtc/webrtc_examples.gyp
@@ -18,7 +18,7 @@
             '<(DEPTH)/third_party/icu/icu.gyp:icuuc',
             '<(webrtc_root)/modules/modules.gyp:video_capture_module_internal_impl',
 	    '<(webrtc_root)/modules/modules.gyp:video_render_module_internal_impl',
-            '<(webrtc_root)/system_wrappers/source/system_wrappers.gyp:field_trial_default',
+            '<(webrtc_root)/system_wrappers/source/system_wrappers.gyp:system_wrappers_default',
             '<(webrtc_root)/test/test.gyp:channel_transport',
             '<(webrtc_root)/video_engine/video_engine.gyp:video_engine_core',
             '<(webrtc_root)/voice_engine/voice_engine.gyp:voice_engine',