[Android] Add configurations for cronet continuous builder + trybot.

testing/buildbot/chromium.android.json

 {
-  "Android GN Builder (dbg)": {
+  "Android Cronet Builder": {
     "additional_compile_targets": [
-      "blimp_tests",
-      "chrome_public_apk",
-      "chrome_public_test_apk",
-      "content_shell_apk",
-      "content_shell_test_apk",
-      "mojo_test_apk",
-      "system_webview_apk"
+      "cronet"

[xunjieli, 2016/09/02 18:21:02]

Can we compile "cronet_package" target? which will compile all dependent targets
like :cronet, :cronet_api, etc.

[jbudorick, 2016/09/02 18:27:19]

ah, yeah. Done.

     ]
   },
   "Android N5X Swarm Builder": {
     "gtest_tests": [
       {
         "override_compile_targets": [
           "android_webview_test_apk"
         ],
         "override_isolate_target": "android_webview_test_apk",
         "swarming": {
@@ skipping 3197 matching lines @@
       },
       {
         "test": "chrome_sync_shell_test_apk"
       },
       {
         "test": "content_shell_test_apk"
       }
     ]
   }
 }