[Telemetry] Add the ability to flush the system file cache to platform.

tools/telemetry/telemetry/core/platform/__init__.py

Index: tools/telemetry/telemetry/core/platform/__init__.py
diff --git a/tools/telemetry/telemetry/core/platform/__init__.py b/tools/telemetry/telemetry/core/platform/__init__.py
index f9a3dffb5a5e398356aedd10cfd3dd0ffb9def4c..5b88286cfa81acd5a52e23f59b31964540f4b090 100644
--- a/tools/telemetry/telemetry/core/platform/__init__.py
+++ b/tools/telemetry/telemetry/core/platform/__init__.py
@@ -84,3 +84,23 @@ class Platform(object):
 
     Examples: VISTA, WIN7, LION, MOUNTAINLION"""
     return self._platform_backend.GetOSVersionName()
+
+  def CanFlushIndividualFilesFromSystemCache(self):
+    """Returns true if the disk cache can be flushed for specific files."""
+    return self._platform_backend.CanFlushIndividualFilesFromSystemCache()
+
+  def FlushEntireSystemCache(self):
+    """Flushes the OS's file cache completely.
+
+    This function may require root or administrator access."""
+    return self._platform_backend.FlushEntireSystemCache()
+
+  def FlushSystemCacheForDirectory(self, directory, ignoring=None):
+    """Flushes the OS's file cache for the specified directory.
+
+    Any files or directories inside |directory| matching a name in the
+    |ignoring| list will be skipped.
+
+    This function does not require root or administrator access."""
+    return self._platform_backend.FlushSystemCacheForDirectory(
+        directory, ignoring=ignoring)