Revert of [Telemetry] Always use ephemeral port chosen by Chrome.

tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py

Index: tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py b/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
index 5fa7a04f0185d9df326c08001ef9153325445031..19836151f4b6f17be064e8cddf0448c31462897b 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/desktop_browser_backend.py
@@ -76,16 +76,17 @@
         logging.info("Using profile directory:'%s'." % profile_dir)
         shutil.rmtree(self._tmp_profile_dir)
         shutil.copytree(profile_dir, self._tmp_profile_dir)
-    # No matter whether we're using an existing profile directory or
-    # creating a new one, always delete the well-known file containing
-    # the active DevTools port number.
-    port_file = self._GetDevToolsActivePortPath()
-    if os.path.isfile(port_file):
-      try:
-        os.remove(port_file)
-      except Exception as e:
-        logging.critical('Unable to remove DevToolsActivePort file: %s' % e)
-        sys.exit(1)
+    if self.browser_options.use_devtools_active_port:
+      # No matter whether we're using an existing profile directory or
+      # creating a new one, always delete the well-known file containing
+      # the active DevTools port number.
+      port_file = self._GetDevToolsActivePortPath()
+      if os.path.isfile(port_file):
+        try:
+          os.remove(port_file)
+        except Exception as e:
+          logging.critical('Unable to remove DevToolsActivePort file: %s' % e)
+          sys.exit(1)
 
   def _GetDevToolsActivePortPath(self):
     return os.path.join(self.profile_directory, 'DevToolsActivePort')
@@ -129,33 +130,37 @@
     if not self.IsBrowserRunning():
       raise exceptions.ProcessGoneException(
           "Return code: %d" % self._proc.returncode)
-    # The Telemetry user selected the new code path to start DevTools on
-    # an ephemeral port. Wait for the well-known file containing the port
-    # number to exist.
-    port_file = self._GetDevToolsActivePortPath()
-    if not os.path.isfile(port_file):
-      # File isn't ready yet. Return false. Will retry.
-      return False
-    # Attempt to avoid reading the file until it's populated.
-    got_port = False
-    try:
-      if os.stat(port_file).st_size > 0:
-        with open(port_file) as f:
-          port_string = f.read()
-          self._port = int(port_string)
-          logging.info('Discovered ephemeral port %s' % self._port)
-          got_port = True
-    except Exception:
-      # Both stat and open can throw exceptions.
-      pass
-    if not got_port:
-      # File isn't ready yet. Return false. Will retry.
-      return False
+    if self.browser_options.use_devtools_active_port:
+      # The Telemetry user selected the new code path to start DevTools on
+      # an ephemeral port. Wait for the well-known file containing the port
+      # number to exist.
+      port_file = self._GetDevToolsActivePortPath()
+      if not os.path.isfile(port_file):
+        # File isn't ready yet. Return false. Will retry.
+        return False
+      # Attempt to avoid reading the file until it's populated.
+      got_port = False
+      try:
+        if os.stat(port_file).st_size > 0:
+          with open(port_file) as f:
+            port_string = f.read()
+            self._port = int(port_string)
+            logging.info('Discovered ephemeral port %s' % self._port)
+            got_port = True
+      except Exception:
+        # Both stat and open can throw exceptions.
+        pass
+      if not got_port:
+        # File isn't ready yet. Return false. Will retry.
+        return False
     return super(DesktopBrowserBackend, self).HasBrowserFinishedLaunching()
 
   def GetBrowserStartupArgs(self):
     args = super(DesktopBrowserBackend, self).GetBrowserStartupArgs()
-    self._port = 0
+    if self.browser_options.use_devtools_active_port:
+      self._port = 0
+    else:
+      self._port = util.GetUnreservedAvailableLocalPort()
     logging.info('Requested remote debugging port: %d' % self._port)
     args.append('--remote-debugging-port=%i' % self._port)
     args.append('--enable-crash-reporter-for-testing')