[processor] Infer the channel label from reports

When the uploader does not provide a channel label, the processor will
now set it based on a new property in the report,
`run_info.browser_channel`, introduced in
web-platform-tests/wpt#12679 .

A new channel label, "beta", is also introduced in this commit, since we
now have beta browsers running on Taskcluster daily.

results-processor/wptreport.py

@@ -23,6 +23,15 @@
 
 DEFAULT_PROJECT = 'wptdashboard'
 GCS_PUBLIC_DOMAIN = 'https://storage.googleapis.com'
+CHANNEL_TO_LABEL = {
+    'release': 'stable',
+    'stable': 'stable',
+    'beta': 'beta',
+    'dev': 'experimental',
+    'experimental': 'experimental',
+    'nightly': 'experimental',
+    'preview': 'experimental',
+}
 
 _log = logging.getLogger(__name__)
 
@@ -429,8 +438,7 @@ def prepare_labels(report, labels_str, uploader):
     The following labels will be automatically added:
     * The name of the uploader
     * The name of the browser
-    * "stable" (as in release channels), if neither "stable" or "experimental"
-      is provided by the uploader.
+    * The release channel of the browser (if the uploader doesn't provide one)
 
     Args:
         report: A WPTReport.
@@ -446,8 +454,15 @@ def prepare_labels(report, labels_str, uploader):
     # Empty labels may be generated here, but they will be removed later.
     for label in labels_str.split(','):
         labels.add(label.strip())
-    if ('stable' not in labels) and ('experimental' not in labels):
-        labels.add('stable')
+
+    # Add the release channel label.
+    if not any([i in labels for i in set(CHANNEL_TO_LABEL.values())]):
+        if report.run_info.get('browser_channel') in CHANNEL_TO_LABEL:
+            labels.add(CHANNEL_TO_LABEL[report.run_info['browser_channel']])
+        else:
+            # Default to "stable".
+            labels.add('stable')
+
     # Remove any empty labels.
     if '' in labels:
         labels.remove('')

results-processor/wptreport_test.py

@@ -505,3 +505,8 @@ def test_prepare_labels_from_browser_channel(self):
             prepare_labels(r, '', 'blade-runner'),
             ['blade-runner', 'experimental', 'firefox']
         )
+        r._report['run_info']['browser_channel'] = 'beta'
+        self.assertListEqual(
+            prepare_labels(r, '', 'blade-runner'),
+            ['beta', 'blade-runner', 'firefox']
+        )