Creates a BattOrConnection for communicating with the BattOr

tools/battor_agent/battor_agent_bin.cc

Index: tools/battor_agent/battor_agent_bin.cc
diff --git a/tools/battor_agent/battor_agent_bin.cc b/tools/battor_agent/battor_agent_bin.cc
index 26c855c6e870107755917d4f2e70524799f53ce0..5843ae906b10f6e3f97aaf7075808cda945e38ef 100644
--- a/tools/battor_agent/battor_agent_bin.cc
+++ b/tools/battor_agent/battor_agent_bin.cc
@@ -49,7 +49,7 @@ void PrintSupportsExplicitClockSync() {
 std::string GetArg(int argnum, int argc, char* argv[]) {
   if (argnum >= argc) {
     PrintUsage();
-    PLOG(FATAL);
+    exit(1);
   }
 
   return argv[argnum];
@@ -58,16 +58,13 @@ std::string GetArg(int argnum, int argc, char* argv[]) {
 // Checks if an error occurred and, if it did, prints the error and exits
 // with an error code.
 void CheckError(battor::BattOrError error) {
-  if (error != battor::BATTOR_ERROR_NONE) {
-    LOG(ERROR) << "Fatal error when communicating with the BattOr: " << error;
-    PLOG(FATAL);

[Primiano Tucci (use gerrit), 2015/12/15 11:07:19]

out of cusiosity why are you removing the P here?

[charliea (OOO until 10-5), 2015/12/15 23:50:04]

PLOG just appends the last system error to whatever message I specify. In our
case, a system error wasn't the reason for exiting the program, and may have
been completely unrelated to our program running.

For example, when I did:

  $ cd /this/directory/doesnt/exist

bash: cd: /this/directory/doesnt/exist: No such file or directory

and then:
  $ out/Default/battor_agent StartTracing /dev/nonexistent

I got:
Fatal error when communicating with the BattOr:
cd: /this/directory/doesnt/exist: No such file or directory

Given that we weren't necessarily exiting due to a system error, I think
LOG(FATAL) is probably the way to go

-  }
+  if (error != battor::BATTOR_ERROR_NONE)
+    LOG(FATAL) << "Fatal error when communicating with the BattOr: " << error;
 }
 
 // Prints an error message and exits due to a required thread failing to start.
 void ExitFromThreadStartFailure(const std::string& thread_name) {
-  LOG(ERROR) << "Failed to start " << thread_name;
-  PLOG(FATAL);
+  LOG(FATAL) << "Failed to start " << thread_name;
 }
 
 }  // namespace
@@ -84,9 +81,7 @@ class BattOrAgentBin : public BattOrAgent::Listener {
         file_thread_(kFileThreadName),
         ui_thread_(kUiThreadName) {}
 
-  ~BattOrAgentBin() {
-    DCHECK(!agent_);
-  }
+  ~BattOrAgentBin() { DCHECK(!agent_); }
 
   // Runs the BattOr binary and returns the exit code.
   int Run(int argc, char* argv[]) {