Move PageTest.ValidatePageSet special-case into profile creator.

tools/perf/profile_creators/small_profile_creator.py

Index: tools/perf/profile_creators/small_profile_creator.py
diff --git a/tools/perf/profile_creators/small_profile_creator.py b/tools/perf/profile_creators/small_profile_creator.py
index 46109a7a4f341a536c73cb5e47498f07a2c37085..a63cca894fdc75d5831a729e52116232c030288c 100644
--- a/tools/perf/profile_creators/small_profile_creator.py
+++ b/tools/perf/profile_creators/small_profile_creator.py
@@ -24,11 +24,21 @@ class SmallProfileCreator(profile_creator.ProfileCreator):
     def __init__(self):
       super(SmallProfileCreator.PageTest, self).__init__()
       self._page_set = page_sets.Typical25PageSet()
+      self._ValidatePageSet(self._page_set)
 
       # Open all links in the same tab save for the last _NUM_TABS links which
       # are each opened in a new tab.
       self._NUM_TABS = 5
 
+    @staticmethod
+    def _ValidatePageSet(page_set):
+      """Raise an exception if |page_set| uses more than one WPR archive."""
+      wpr_paths = set(page_set.WprFilePathForUserStory(p)
+                      for p in page_set if not p.is_local)
+      if len(wpr_paths) > 1:
+        raise Exception("Invalid page set: has multiple WPR archives: %s" %
+                        ','.join(sorted(wpr_paths)))
+
     def TabForPage(self, page, browser):
       """Superclass override."""
       idx = page.page_set.pages.index(page)