Bug 1188444 - Handle the common StepParser parser case first

Normal log lines (ie not step marker lines) are the most common. Handle
this case first to improve performance and simplify the later
conditionals.

treeherder/log_parser/parsers.py

@@ -108,26 +108,31 @@ def parse_line(self, line, lineno):
         """
         step_marker_match = self.RE_STEP_MARKER.match(line)
 
+        if not step_marker_match:
+            # This is a normal log line, rather than a step marker. (The common case.)
+            # Parse the line for errors, which if found, will be associated with the current step.
+            self.sub_parser.parse_line(line, lineno)
+            return
+
+        # This is either a "step started" or "step finished" marker line, eg:
+        # ========= Started foo (results: 0, elapsed: 0 secs) (at 2015-08-17 02:33:56.353866) =========
+        # ========= Finished foo (results: 0, elapsed: 0 secs) (at 2015-08-17 02:33:56.354301) =========
+
         # Check if we're waiting for a step start line.
         if self.state != self.STATES['step_in_progress']:
             # Start a new step using the extracted step metadata.
-            if step_marker_match and step_marker_match.group('marker_type') == 'Started':
+            if step_marker_match.group('marker_type') == 'Started':
                 self.start_step(lineno,
                                 name=step_marker_match.group('name'),
                                 timestamp=step_marker_match.group('timestamp'))
             return
 
         # Check if it's the end of a step.
-        if step_marker_match and step_marker_match.group('marker_type') == 'Finished':
+        if step_marker_match.group('marker_type') == 'Finished':
             # Close out the current step using the extracted step metadata.
             self.end_step(lineno,
                           timestamp=step_marker_match.group('timestamp'),
                           result_code=int(step_marker_match.group('result_code')))
-            return
-
-        # This is a normal log line, rather than a step marker. (The common case.)
-        # Parse the line for errors, which if found, will be associated with the current step.
-        self.sub_parser.parse_line(line, lineno)
 
     def start_step(self, lineno, name="Unnamed step", timestamp=None):
         """Create a new step and update the state to reflect we're now in the middle of a step."""