Fix handling multiple repeats in wptreport logs

Previously this would have ended up with multiple JSON objects all put
on the same line and we'd be unable to update from such
metadata. Ensure that there's one line per JSON object and the update
code is able to consume this format.

Differential Revision: https://phabricator.services.mozilla.com/D47248

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1584192
gecko-commit: 83dc6a6ed93137707ecfd785f10a721e2e1abca7
gecko-integration-branch: autoland
gecko-reviewers: maja_zf

Author: jgraham

tools/wptrunner/wptrunner/formatters/wptreport.py

@@ -70,7 +70,7 @@ def suite_end(self, data):
             result = {"test": test_name}
             result.update(self.raw_results[test_name])
             self.results["results"].append(result)
-        return json.dumps(self.results)
+        return json.dumps(self.results) + "\n"
 
     def find_or_create_test(self, data):
         test_name = data["test"]

tools/wptrunner/wptrunner/metadata.py

@@ -353,18 +353,40 @@ def __init__(self, id_test_map):
         self.tests_visited = {}
 
     def update_from_log(self, log_file):
+        # We support three possible formats:
+        # * wptreport format; one json object in the file, possibly pretty-printed
+        # * wptreport format; one run per line
+        # * raw log format
+
+        # Try one wptreport file first
         self.run_info = None
+        success = self.get_wptreport_data(log_file.read())
+
+        if success:
+            return
+
+        # Now try multiple wptreport files
+        log_file.seek(0)
+        for line in log_file:
+            success = self.get_wptreport_data(line)
+            if not success:
+                break
+        else:
+            return
+
+        log_file.seek(0)
+        self.update_from_raw_log(log_file)
+
+    def get_wptreport_data(self, input_str):
         try:
-            data = json.load(log_file)
+            data = json.loads(input_str)
         except Exception:
             pass
         else:
             if "action" not in data and "results" in data:
                 self.update_from_wptreport_log(data)
-                return
-
-        log_file.seek(0)
-        self.update_from_raw_log(log_file)
+                return True
+        return False
 
     def update_from_raw_log(self, log_file):
         action_map = self.action_map