[Telemetry] Reorganize everything.

tools/telemetry/telemetry/core/exceptions.py

-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 class BrowserGoneException(Exception):
   """Represents a crash of the entire browser.
 
   In this state, all bets are pretty much off."""
   pass
 
 class BrowserConnectionGoneException(BrowserGoneException):
   pass
+
+class TabCrashException(Exception):
+  """Represents a crash of the current tab, but not the overall browser.
+
+  In this state, the tab is gone, but the underlying browser is still alive."""
+  pass
+
+class EvaluateException(Exception):
+  pass