Implement FlushSystemCacheForDirectory for Chrome OS

tools/telemetry/telemetry/core/platform/desktop_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/desktop_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/desktop_platform_backend.py b/tools/telemetry/telemetry/core/platform/desktop_platform_backend.py
index 9a5b9224df5f53f0ce889ea223caed286aa0bd04..bbfb5fff5795871cb2428054a780b9531d3f023f 100644
--- a/tools/telemetry/telemetry/core/platform/desktop_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/desktop_platform_backend.py
@@ -14,7 +14,7 @@ class DesktopPlatformBackend(platform_backend.PlatformBackend):
   # This is an abstract class. It is OK to have abstract methods.
   # pylint: disable=W0223
 
-  def FlushSystemCacheForDirectory(self, directory, ignoring=None):
+  def FlushSystemCacheForDirectory(self, directory):
     assert directory and os.path.exists(directory), \
         'Target directory %s must exist' % directory
     flush_command = support_binaries.FindPath('clear_system_cache',
@@ -22,19 +22,4 @@ class DesktopPlatformBackend(platform_backend.PlatformBackend):
                                               self.GetOSName())
     assert flush_command, 'You must build clear_system_cache first'
 
-    args = []
-    directory_contents = os.listdir(directory)
-    for item in directory_contents:
-      if not ignoring or item not in ignoring:
-        args.append(os.path.join(directory, item))
-
-    # According to msdn:
-    # http://msdn.microsoft.com/en-us/library/ms682425%28VS.85%29.aspx
-    # there's a maximum allowable command line of 32,768 characters on windows.
-    while args:
-      # Small note about [:256] and [256:]
-      # [:N] will return a list with the first N elements, ie.
-      # with [1,2,3,4,5], [:2] -> [1,2], and [2:] -> [3,4,5]
-      # with [1,2,3,4,5], [:5] -> [1,2,3,4,5] and [5:] -> []
-      subprocess.check_call([flush_command, '--recurse'] + args[:256])
-      args = args[256:]
+    subprocess.check_call([flush_command, '--recurse', directory])