[telemetry] Prototype for specifying page sets using Python imports and Telemetry discovery.

tools/telemetry/telemetry/test.py

Index: tools/telemetry/telemetry/test.py
diff --git a/tools/telemetry/telemetry/test.py b/tools/telemetry/telemetry/test.py
index 5f52affb9910e1c747bd5dc1b0d84e502f9fc860..10dc5cd47a58f8c7f0233ce6f9865d92bfd450c2 100644
--- a/tools/telemetry/telemetry/test.py
+++ b/tools/telemetry/telemetry/test.py
@@ -38,7 +38,11 @@ class Test(command_line.Command):
     if hasattr(cls, 'tag'):
       name += '.' + cls.tag
     if hasattr(cls, 'page_set'):
-      name += '.' + os.path.basename(os.path.splitext(cls.page_set)[0])
+      if isinstance(cls.page_set, basestring):
+        # TODO(dtu): Remove this code path after crbug.com/362293.
+        name += '.' + os.path.basename(os.path.splitext(cls.page_set)[0])
+      else:
+        name += '.' + cls.page_set.Name()
     return name
 
   @classmethod
@@ -164,16 +168,25 @@ class Test(command_line.Command):
     return cls.test
 
   @classmethod
+  def PageSetClass(cls):
+    """Get the PageSet for this Test.
+
+    If the Test has no PageSet, raises NotImplementedError.
+    """
+    if not hasattr(cls, 'page_set'):
+      raise NotImplementedError('This test has no "page_set" attribute.')
+    if not issubclass(cls.page_set, page_set.PageSet):
+      raise TypeError('"%s" is not a PageSet.' % cls.page_set.__name__)
+    return cls.page_set
+
+  @classmethod
   def CreatePageSet(cls, options):  # pylint: disable=W0613
     """Get the page set this test will run on.
 
     By default, it will create a page set from the file at this test's
     page_set attribute. Override to generate a custom page set.
     """
-    if not hasattr(cls, 'page_set'):
-      raise NotImplementedError('This test has no "page_set" attribute.')
-    return page_set.PageSet.FromFile(
-        file_path=os.path.join(util.GetBaseDir(), cls.page_set))
+    return cls.PageSetClass()()
 
   @classmethod
   def CreateExpectations(cls, ps):  # pylint: disable=W0613