Android GTest Runner: Don't clear app data for incremental installs

build/android/pylib/local/device/local_device_gtest_run.py

 # Copyright 2014 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.
 
 import imp
 import itertools
 import os
 import posixpath
 
 from devil.android import device_errors
@@ skipping 288 matching lines @@
     # Run the test.
     timeout = (self._test_instance.shard_timeout
                * self.GetTool(device).GetTimeoutScale())
     output = self._delegate.Run(
         test, device, timeout=timeout, retries=0)
     for s in self._servers[str(device)]:
       s.Reset()
     if self._test_instance.app_files:
       self._delegate.PullAppFiles(device, self._test_instance.app_files,
                                   self._test_instance.app_file_dir)
-    self._delegate.Clear(device)
+    # Clearing data when using incremental install wipes out cached optimized
+    # dex files (and shouldn't be necessary by tests anyways).
+    if not self._env.incremental_install:
+      self._delegate.Clear(device)
 
     # Parse the output.
     # TODO(jbudorick): Transition test scripts away from parsing stdout.
     results = self._test_instance.ParseGTestOutput(output)
     return results
 
   #override
   def TearDown(self):
     @local_device_test_run.handle_shard_failures
     def individual_device_tear_down(dev):
       for s in self._servers.get(str(dev), []):
         s.TearDown()
 
       tool = self.GetTool(dev)
       tool.CleanUpEnvironment()
 
     self._env.parallel_devices.pMap(individual_device_tear_down)