Implement GetSystemLog on Linux platform

telemetry/telemetry/internal/platform/linux_platform_backend.py

Index: telemetry/telemetry/internal/platform/linux_platform_backend.py
diff --git a/telemetry/telemetry/internal/platform/linux_platform_backend.py b/telemetry/telemetry/internal/platform/linux_platform_backend.py
index 7efb05db5e41c42e67aec7ad90442c6720a04362..01aa0b8bbc60b908811dbe2e622da1bc619d76e7 100644
--- a/telemetry/telemetry/internal/platform/linux_platform_backend.py
+++ b/telemetry/telemetry/internal/platform/linux_platform_backend.py
@@ -72,6 +72,11 @@ class LinuxPlatformBackend(
   def GetOSVersionDetailString(self):
     return ''  # TODO(kbr): Implement this.
 
+  def GetSystemLog(self):
+    # Since the log file can be very large, only show the last 200 lines.
+    return subprocess.check_output(
+        ['tail', '-n', '200', '/var/log/syslog'])
+
   def CanFlushIndividualFilesFromSystemCache(self):
     return True