Add cpu_stats for the browser

tools/telemetry/telemetry/core/platform/linux_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/linux_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/linux_platform_backend.py b/tools/telemetry/telemetry/core/platform/linux_platform_backend.py
index 42d6e947a84ecaa6944a35572381e9caeef88979..0cc6be008af29404755b1c9635aa7e6dc6437017 100644
--- a/tools/telemetry/telemetry/core/platform/linux_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/linux_platform_backend.py
@@ -29,6 +29,14 @@ class LinuxPlatformBackend(posix_platform_backend.PosixPlatformBackend):
     meminfo_contents = self._GetFileContents('/proc/meminfo')
     return proc_util.GetSystemCommitCharge(meminfo_contents)
 
+  def GetCpuStats(self, pid=None):
+    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()