Extension profile generator + benchmark for startup with profile.

tools/perf/profile_creators/profile_extender.py

Index: tools/perf/profile_creators/profile_extender.py
diff --git a/tools/perf/profile_creators/profile_extender.py b/tools/perf/profile_creators/profile_extender.py
index 22ace38fbe5ad168be2f39b89fd5555c551b1a3e..95b9fb0f55b337bed3254787ec3c7bdc21bd31d2 100644
--- a/tools/perf/profile_creators/profile_extender.py
+++ b/tools/perf/profile_creators/profile_extender.py
@@ -58,6 +58,17 @@ class ProfileExtender(object):
   def browser(self):
     return self._browser
 
+  def EnabledOSList(self):
+    """Returns a list of OSes that this extender can run on.
+
+    Can be overridden by subclasses.
+
+    Returns:
+        List of OS ('win', 'mac', or 'linux') that this extender can run on.
+        None if this extender can run on all platforms.
+    """
+    return None
+
   def SetUpBrowser(self):
     """Finds and starts the browser.
 
@@ -70,6 +81,13 @@ class ProfileExtender(object):
     """
     possible_browser = self._GetPossibleBrowser(self.finder_options)
 
+    os_name = possible_browser.platform.GetOSName()
+    enabled_os_list = self.EnabledOSList()
+    if enabled_os_list is not None and os_name not in enabled_os_list:
+      raise NotImplementedError(
+        'This profile extender on %s is not yet supported'
+        % os_name)
+
     assert possible_browser.supports_tab_control
     assert (platform.GetHostPlatform().GetOSName() in
         ["win", "mac", "linux"])