apachedex: Rename global.

The common unit is microseconds. While this value was correct, its name
was misleading.

apachedex/__init__.py

@@ -114,7 +114,7 @@ INPUT_ENCODING_ERROR_HANDLER = 'replace'
 MONTH_VALUE_DICT = dict((y, x) for (x, y) in enumerate(('Jan', 'Feb', 'Mar',
   'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'), 1))
 
-MS_PER_S = 10 ** 3
+US_PER_MS = 10 ** 3
 US_PER_S = 10 ** 6
 
 N_HOTTEST_PAGES_DEFAULT = 20
@@ -1384,7 +1384,7 @@ def main():
   if DURATION_US_FORMAT in args.logformat:
     getDuration = lambda x: int(x.group('duration'))
   elif DURATION_MS_FORMAT in args.logformat:
-    getDuration = lambda x: int(x.group('duration_ms')) * MS_PER_S
+    getDuration = lambda x: int(x.group('duration_ms')) * US_PER_MS
   elif DURATION_S_FORMAT in args.logformat:
     getDuration = lambda x: int(x.group('duration_s')) * US_PER_S
   else: