--- a/third_party/rust/mozrunner/.cargo-checksum.json
+++ b/third_party/rust/mozrunner/.cargo-checksum.json
@@ -1,1 +1,1 @@
-{"files":{".cargo-ok":"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855","Cargo.toml":"31f551a8237731c09c51cc0e6823e91ab09f17aa8e58b798e92fb6f2b723f589","LICENSE":"fab3dd6bdab226f1c08630b1dd917e11fcb4ec5e1e020e2c16f83a0a13863e85","src/bin/firefox-default-path.rs":"21f1aa96a4ffb368a4266e294bc4b1b17ff8229f2418af6679783f6d9c0280df","src/lib.rs":"26ea358c4bc1d45eb3b5ebc702b1a6bffdf5642acab9bbeffddb5be55ddb1b07","src/runner.rs":"c1b94da5424d06a1a233e242d0a2488895e47ed133f8456473871c5a2bb471f1"},"package":"eb9d113eaa876c004ad5119224e318b36fd358658e47cdd49b45d209b2d7ac82"}
\ No newline at end of file
+{"files":{".cargo-ok":"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855","Cargo.toml":"657202ea8600feffb50bf5c1e157a3cb7ddbfaabce8ff4fadb4dfc6bbdcd2663","LICENSE":"fab3dd6bdab226f1c08630b1dd917e11fcb4ec5e1e020e2c16f83a0a13863e85","src/bin/firefox-default-path.rs":"21f1aa96a4ffb368a4266e294bc4b1b17ff8229f2418af6679783f6d9c0280df","src/lib.rs":"26ea358c4bc1d45eb3b5ebc702b1a6bffdf5642acab9bbeffddb5be55ddb1b07","src/runner.rs":"ca015cd994987abd6902c61f9cbcabf760e6f0c0a55b4f16aa8420ab88101eae"},"package":"8ff037ca681fa465d01c863f8b16d4a008997b35468059c06f1a4b828369600b"}
\ No newline at end of file

--- a/third_party/rust/mozrunner/Cargo.toml
+++ b/third_party/rust/mozrunner/Cargo.toml
@@ -7,17 +7,17 @@
 #
 # If you believe there's an error in this file please file an
 # issue against the rust-lang/cargo repository. If you're
 # editing this file be aware that the upstream Cargo.toml
 # will likely look very different (and much more reasonable)
 
 [package]
 name = "mozrunner"
-version = "0.4.2"
+version = "0.5.0"
 authors = ["Mozilla Tools and Automation <auto-tools@mozilla.com>"]
 description = "Library for starting Firefox binaries."
 license = "MPL-2.0"
 repository = "https://github.com/jgraham/rust_mozrunner"
 
 [[bin]]
 name = "firefox-default-path"
 [dependencies.log]

--- a/third_party/rust/mozrunner/src/runner.rs
+++ b/third_party/rust/mozrunner/src/runner.rs
@@ -7,26 +7,22 @@ use std::env;
 use std::error::Error;
 use std::fmt;
 use std::io::{Result as IoResult, Error as IoError, ErrorKind};
 use std::path::{Path, PathBuf};
 use std::process;
 use std::process::{Command, Stdio};
 
 pub trait Runner {
-    fn start(&mut self) -> Result<(), RunnerError>;
-
     fn args(&mut self) -> &mut Vec<String>;
-
     fn build_command(&self, &mut Command);
-
     fn envs(&mut self) -> &mut HashMap<String, String>;
-
-    fn is_running(&self) -> bool;
-
+    fn is_running(&mut self) -> bool;
+    fn start(&mut self) -> Result<(), RunnerError>;
+    fn status(&mut self) -> IoResult<Option<process::ExitStatus>>;
     fn stop(&mut self) -> IoResult<Option<process::ExitStatus>>;
 }
 
 #[derive(Debug)]
 pub enum RunnerError {
     Io(IoError),
     PrefReader(PrefReaderError),
 }
@@ -65,22 +61,22 @@ impl From<IoError> for RunnerError {
 }
 
 impl From<PrefReaderError> for RunnerError {
     fn from(value: PrefReaderError) -> RunnerError {
         RunnerError::PrefReader(value)
     }
 }
 
+#[derive(Debug)]
 pub struct FirefoxRunner {
     pub binary: PathBuf,
     args: Vec<String>,
     envs: HashMap<String, String>,
     process: Option<process::Child>,
-    pub ret_code: Option<process::ExitStatus>,
     pub profile: Profile
 }
 
 impl FirefoxRunner {
     pub fn new(binary: &Path, profile: Option<Profile>) -> IoResult<FirefoxRunner> {
         let prof = match profile {
             Some(p) => p,
             None => try!(Profile::new(None))
@@ -88,39 +84,24 @@ impl FirefoxRunner {
 
         let mut envs = HashMap::new();
         envs.insert("MOZ_NO_REMOTE".to_string(), "1".to_string());
         envs.insert("NO_EM_RESTART".to_string(), "1".to_string());
 
         Ok(FirefoxRunner {
             binary: binary.to_path_buf(),
             process: None,
-            ret_code: None,
             args: Vec::new(),
             envs: envs,
             profile: prof
         })
     }
 }
 
 impl Runner for FirefoxRunner {
-    fn start(&mut self) -> Result<(), RunnerError> {
-        let mut cmd = Command::new(&self.binary);
-        self.build_command(&mut cmd);
-
-        debug!("Command {:?}", cmd);
-
-        let prefs = try!(self.profile.user_prefs());
-        try!(prefs.write());
-
-        let process = try!(cmd.spawn());
-        self.process = Some(process);
-        Ok(())
-    }
-
     fn args(&mut self) -> &mut Vec<String> {
         &mut self.args
     }
 
     fn build_command(&self, command: &mut Command) {
         command
             .args(&self.args[..])
             .envs(&self.envs);
@@ -131,27 +112,45 @@ impl Runner for FirefoxRunner {
         command.stdout(Stdio::inherit())
             .stderr(Stdio::inherit());
     }
 
     fn envs(&mut self) -> &mut HashMap<String, String> {
         &mut self.envs
     }
 
-    fn is_running(&self) -> bool {
-        self.process.is_some() && self.ret_code.is_none()
+    fn is_running(&mut self) -> bool {
+        self.process.is_some() && self.status().unwrap().is_none()
+    }
+
+    fn start(&mut self) -> Result<(), RunnerError> {
+        let mut cmd = Command::new(&self.binary);
+        self.build_command(&mut cmd);
+
+        let prefs = try!(self.profile.user_prefs());
+        try!(prefs.write());
+
+        info!("Running command: {:?}", cmd);
+        let process = try!(cmd.spawn());
+        self.process = Some(process);
+        Ok(())
+    }
+
+    fn status(&mut self) -> IoResult<Option<process::ExitStatus>> {
+        self.process.as_mut().map(|p| p.try_wait()).unwrap_or(Ok(None))
     }
 
     fn stop(&mut self) -> IoResult<Option<process::ExitStatus>> {
-        if let Some(p) = self.process.as_mut() {
+        let mut retval = None;
+
+        if let Some(ref mut p) = self.process {
             try!(p.kill());
-            let status = try!(p.wait());
-            self.ret_code = Some(status);
+            retval = Some(try!(p.wait()));
         };
-        Ok(self.ret_code)
+        Ok(retval)
     }
 }
 
 fn parse_arg_name(arg: &str) -> Option<&str> {
     let mut start = 0;
     let mut end = 0;
 
     for (i, c) in arg.chars().enumerate() {