Telemetry: Add option to create a dirty profile as part of a test run

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

Index: tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py
diff --git a/tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py b/tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py
index 58a6307fd613191fe687b197f3bb8ec7bb357dc7..6d89542e83a3d247ba1dacb033fcacd64360105d 100644
--- a/tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py
+++ b/tools/telemetry/telemetry/core/chrome/desktop_browser_backend.py
@@ -16,10 +16,12 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
   """The backend for controlling a locally-executed browser instance, on Linux,
   Mac or Windows.
   """
-  def __init__(self, options, executable, is_content_shell, use_login):
+  def __init__(self, options, executable, is_content_shell, use_login,
+               delete_profile_dir_after_run=True):
     super(DesktopBrowserBackend, self).__init__(
         is_content_shell=is_content_shell,
-        supports_extensions=not is_content_shell, options=options)
+        supports_extensions=not is_content_shell,
+        options=options)
 
     # Initialize fields so that an explosion during init doesn't break in Close.
     self._proc = None
@@ -37,7 +39,9 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
           'Content shell does not support extensions.')
 
     self._port = util.GetAvailableLocalPort()
+    self._profile_dir = None
     self._supports_net_benchmarking = True
+    self._delete_profile_dir_after_run = delete_profile_dir_after_run
     self._LaunchBrowser(options)
 
     # For old chrome versions, might have to relaunch to have the
@@ -78,6 +82,7 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
         args.append('--enable-benchmarking')
       if not self.options.dont_override_profile:
         self._tmpdir = tempfile.mkdtemp()
+        self._profile_dir = self._tmpdir
         if self.options.profile_dir:
           if self.is_content_shell:
             logging.critical('Profiles cannot be used with content shell')
@@ -98,6 +103,10 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
       return self._proc.pid
     return None
 
+  @property
+  def profile_directory(self):
+    return self._profile_dir
+
   def IsBrowserRunning(self):
     return self._proc.poll() == None
 
@@ -141,7 +150,8 @@ class DesktopBrowserBackend(browser_backend.BrowserBackend):
           self._proc = None
           raise Exception('Could not shutdown the browser.')
 
-    if self._tmpdir and os.path.exists(self._tmpdir):
+    if self._delete_profile_dir_after_run and \
+        self._tmpdir and os.path.exists(self._tmpdir):
       shutil.rmtree(self._tmpdir, ignore_errors=True)
       self._tmpdir = None