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

tools/telemetry/telemetry/core/platform/win_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/win_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/win_platform_backend.py b/tools/telemetry/telemetry/core/platform/win_platform_backend.py
index f002c1037c1703b4af462c09c4277e9f2d64bb8e..71038ecb60498c8224de6a8ff76d5c47cf8df851 100644
--- a/tools/telemetry/telemetry/core/platform/win_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/win_platform_backend.py
@@ -18,10 +18,10 @@ except ImportError:
   win32con = None
   win32process = None
 
-from telemetry.core.platform import platform_backend
+from telemetry.core.platform import desktop_platform_backend
 
 
-class WinPlatformBackend(platform_backend.PlatformBackend):
+class WinPlatformBackend(desktop_platform_backend.DesktopPlatformBackend):
   def _GetProcessHandle(self, pid):
     mask = (win32con.PROCESS_QUERY_INFORMATION |
             win32con.PROCESS_VM_READ)
@@ -159,3 +159,9 @@ class WinPlatformBackend(platform_backend.PlatformBackend):
       return 'win7'
     if os_version.startswith('6.2.'):
       return 'win8'
+
+  def CanFlushIndividualFilesFromSystemCache(self):
+    return True
+
+  def GetFlushUtilityName(self):
+    return 'clear_system_cache.exe'