headless: Also build the headless shell target on the bot

testing/buildbot/chromium.fyi.json

 {
   "Android Asan Builder Tests (dbg)": {
     "gtest_tests": [
       {
         "args": [
           "--tool=asan"
         ],
         "test": "android_webview_unittests"
       },
       {
@@ skipping 8984 matching lines @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "wtf_unittests"
       }
     ]
   },
   "Headless Linux (dbg)": {
     "additional_compile_targets": [
       "headless_lib",
+      "headless_shell",

[Ken Russell (switch to Gerrit), 2016/08/15 20:26:56]

In general it would be better for this to be built as a dependency of one of the
test targets that are run on this machine. Is that the long-term plan?

[Sami, 2016/08/16 09:40:58]

The problem is that none of the headless unit or browser tests actually need the
headless shell app to run; it's more of an interactive tool for developers. The
app will ultimately go away once we teach Chrome itself to become headless, but
for now it's useful to have around.

       "headless_tests"
     ],
     "gtest_tests": [
       {
         "test": "headless_browsertests"
       },
       {
         "test": "headless_unittests"
       }
     ]
@@ skipping 2522 matching lines @@
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "views_unittests"
       }
     ]
   }
 }