[Telemetry] Dynamically set remote debugging port in DesktopBrowserBackend.

tools/telemetry/telemetry/desktop_browser_backend.py

Index: tools/telemetry/telemetry/desktop_browser_backend.py
diff --git a/tools/telemetry/telemetry/desktop_browser_backend.py b/tools/telemetry/telemetry/desktop_browser_backend.py
index 43ac0b5c1588aa830486a146afd33c6a873e14d1..a0e3d457e4eca004084bd74bf6bc681048bc872b 100644
--- a/tools/telemetry/telemetry/desktop_browser_backend.py
+++ b/tools/telemetry/telemetry/desktop_browser_backend.py
@@ -9,8 +9,6 @@ import tempfile
 from telemetry import browser_backend
 from telemetry import util
 
-DEFAULT_PORT = 9273
-
 class DesktopBrowserBackend(browser_backend.BrowserBackend):
   """The backend for controlling a locally-executed browser instance, on Linux,
   Mac or Windows.
@@ -27,7 +25,8 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
     if not self._executable:
       raise Exception('Cannot create browser, no executable found!')
 
-    self._port = DEFAULT_PORT
+    self._port = util.GetAvailableLocalPort()
+
     args = [self._executable]
     args.extend(self.GetBrowserStartupArgs())
     if not options.show_stdout: