Implement cpu_stats for cros backend

tools/telemetry/telemetry/core/platform/cros_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/cros_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/cros_platform_backend.py b/tools/telemetry/telemetry/core/platform/cros_platform_backend.py
index af2312f6525d4e321f0d104c00d08a91196e9c6b..62e37875d25eff0380e5c7889392e7c2f491a847 100644
--- a/tools/telemetry/telemetry/core/platform/cros_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/cros_platform_backend.py
@@ -40,6 +40,14 @@ class CrosPlatformBackend(platform_backend.PlatformBackend):
     meminfo_contents = self._GetFileContents('/proc/meminfo')
     return proc_util.GetSystemCommitCharge(meminfo_contents)
 
+  def GetCpuStats(self, pid):
+    stats = self._GetFileContents('/proc/%s/stat' % pid).split()
+    return proc_util.GetCpuStats(stats)
+
+  def GetCpuTimestamp(self):
+    timer_list = self._GetFileContents('/proc/timer_list')
+    return proc_util.GetTimestampJiffies(timer_list)
+
   def GetMemoryStats(self, pid):
     status = self._GetFileContents('/proc/%s/status' % pid)
     stats = self._GetFileContents('/proc/%s/stat' % pid).split()