Pass camera id into debug_viewer as a flag.

Now, we can match the intrinsics to the camera that the dataset was
captured with.

Change-Id: If8875939eda6126dd5b67f9a41481ffd1bea3260
diff --git a/y2019/vision/BUILD b/y2019/vision/BUILD
index 90c7dff..5cfc52b 100644
--- a/y2019/vision/BUILD
+++ b/y2019/vision/BUILD
@@ -74,7 +74,6 @@
 gtk_dependent_cc_binary(
     name = "debug_viewer",
     srcs = ["debug_viewer.cc"],
-    copts = ["-Wno-unused-variable"],
     restricted_to = VISION_TARGETS,
     deps = [
         ":target_finder",
@@ -83,6 +82,7 @@
         "//aos/vision/blob:transpose",
         "//aos/vision/debug:debug_framework",
         "//aos/vision/math:vector",
+        "@com_github_gflags_gflags//:gflags",
     ],
 )