Add tests for Headless Linux bot

testing/buildbot/chromium.fyi.json

 {
   "Android Cloud Tests": {
     "gtest_tests": [
       {
         "test": "android_webview_unittests"
       },
       {
         "test": "base_unittests"
       },
       {
@@ skipping 6186 matching lines @@
         "test": "webkit_unit_tests"
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "wtf_unittests"
       }
     ]
   },
+  "Headless Linux (dbg)": {
+    "gtest_tests": [
+      {
+        "override_compile_targets": [
+          "headless_libs",
+          "headless_tests"
+        ],
+        "test": "headless_browsertests"

[Dirk Pranke, 2016/04/01 16:56:40]

this change confuses me a bit.

"override_compile_targets" is used when you need to build something other than
what the test name would suggest, i.e., you needed to actually build
"headless_libs" and "headless_tests" in order for "headless_browsertests" to
run.

But, I don't think that's the case, right?

If what you want is to build "headless_libs" and "headless_tests" *in addition
to* "headless_browsertests", put those two in a list called
"additional_compile_targets" at the top level, next to "gtest_tests".

[perezju, 2016/04/04 11:32:46]

Done. But just to double-check (because I'm not very familiar with these areas),
on the recipe side the compile step seems to include "All" and
"chromium_builder_tests" targets.
https://chromium.googlesource.com/chromium/tools/build/+/master/scripts/slave...

Is the change on 'additional_compile_targets' overriding that setting? Or do I
need to make another change on the recipe config for this bot?
https://chromium.googlesource.com/chromium/tools/build/+/master/scripts/slave...

+      }
+    ]
+  },
   "Linux ARM": {
     "gtest_tests": [
       {
         "args": [
           "--gtest_filter=*NaCl*.*"
         ],
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "browser_tests"
@@ skipping 1480 matching lines @@
       },
       {
         "args": [
           "--isolate-extensions"
         ],
         "test": "unit_tests"
       }
     ]
   }
 }