Merge all Field Trial Testing Configuration Together

tools/variations/unittest_data/test_config.json

 {
   "TestTrial1": [
-    {"group_name": "TestGroup1"}
+    {
+      "groups": [{"group_name": "TestGroup1"}],
+      "platforms": ["win"]
+    }
   ],
   "TestTrial2": [
     {
-      "group_name": "TestGroup2",
-      "params": {
-        "x": "1",
-        "y": "2"
-      },
-      "enable_features": ["A", "B"],
-      "disable_features": ["C"]
-    },
-    {
-      "group_name": "TestGroup2-2",
-      "params": {
-        "x": "3",
-        "y": "4"
-      },
-      "enable_features": ["D", "E"],
-      "disable_features": ["F"]
+      "groups": [

[Alexei Svitkine (slow), 2016/08/30 17:59:15]

We call these "experiments" server-side. How about keeping the same naming
convention here?

[robliao, 2016/08/30 18:16:43]

jwd suggested that the terminiology was trial and group.
https://codereview.chromium.org/2259443003/diff/40001/chrome/common/variation...

If we called these experiments, we would call all of these studies (which is
partially what I had in the previous CL that packaged all of the groups in C++).

What's the preferred terminology for field trials in Chromium?

[Alexei Svitkine (slow), 2016/08/30 21:39:50]

It's a tricky question and I can see arguments for both sides.

In this case, given this is making the name more prominent to users, I think
making it more consistent with server-side terminology makes more sense.

It's true that FieldTrial API uses "group" terminology, but it's also true that
almost no one actually uses APIs that use that terminology - i.e. base::Feature
or variation params is preferred these days and even when raw field trials are
used, the API is usually FindFullName() which doesn't mention group.

So my suggestion is to go with "study"/"experiments" just like server-side
configs. I would also rename "group_name" field to just "name" now that "groups"
is being spelled out explicitly. This way, the config actually becomes a subset
of the server-side config, essentially.

[robliao, 2016/09/01 21:49:07]

I made the json format changes. I'd like to adjust the C++ side after this
change to isolate this change to python only.

[robliao, 2016/09/09 00:48:02]

https://codereview.chromium.org/2319293006/
contains the C++ changes.

+        {
+          "group_name": "TestGroup2",
+          "params": {
+            "x": "1",
+            "y": "2"
+          },
+          "enable_features": ["A", "B"],
+          "disable_features": ["C"]
+        },
+        {
+          "group_name": "TestGroup2-2",
+          "params": {
+            "x": "3",
+            "y": "4"
+          },
+          "enable_features": ["D", "E"],
+          "disable_features": ["F"]
+        }
+      ],
+      "platforms": ["win"]

[Alexei Svitkine (slow), 2016/08/30 21:39:50]

Can you list platforms first? This is the convention for server-side configs and
I think will be more natural to our users. (Both here but more importantly in
the actual JSON file.)

[robliao, 2016/09/01 21:49:07]

Done. This also required rewriting the pretty printer.

     }
   ],
   "TestTrial3": [
-    {"group_name": "TestGroup3", "enable_features": ["X"]}
+    {
+      "groups": [{"group_name": "TestGroup3", "enable_features": ["X"]}],
+      "platforms": ["win"]
+    }
   ]
 }