[telemetry] Detect and correct overflow in Intel energy MSRs.

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 11e3195f43f3048826111024164f7f3c6fad9ef6..2ee894ecdc8f85bf62d724cf893d92241ef13cfb 100644
--- a/tools/telemetry/telemetry/core/platform/win_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/win_platform_backend.py
@@ -346,7 +346,7 @@ class WinPlatformBackend(desktop_platform_backend.DesktopPlatformBackend):
       self.CloseMsrServer()
     atexit.register(TerminateProcess, self._msr_server_handle)
 
-  def ReadMsr(self, msr_number):
+  def ReadMsr(self, msr_number, start=0, length=64):
     self._StartMsrServerIfNeeded()
     if not self._msr_server_handle:
       raise OSError('Unable to start MSR server.')
@@ -357,4 +357,4 @@ class WinPlatformBackend(desktop_platform_backend.DesktopPlatformBackend):
       response = sock.recv(8)
     finally:
       sock.close()
-    return struct.unpack('Q', response)[0]
+    return struct.unpack('Q', response)[0] >> start & ((1 << length) - 1)