Add histograms to record raw observations in Network Quality Estimator (NQE).

Bug: 755794
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester
Change-Id: Icd925fb3e597788c1bc3db5beb9ab9a703e012b3
Reviewed-on: https://chromium-review.googlesource.com/636701
Reviewed-by: Jesse Doherty <[email protected]>
Reviewed-by: Ryan Sturm <[email protected]>
Commit-Queue: Tarun Bansal <[email protected]>
Cr-Commit-Position: refs/heads/master@{#498705}
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 6b12f1b6..ea032052 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -1020,6 +1020,7 @@
       "nqe/network_quality_estimator_util.h",
       "nqe/network_quality_observation.cc",
       "nqe/network_quality_observation.h",
+      "nqe/network_quality_observation_source.cc",
       "nqe/network_quality_observation_source.h",
       "nqe/network_quality_provider.cc",
       "nqe/network_quality_provider.h",