[Telemetry] Fix up desktop_browser_finder on Linux

tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py

Index: tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py
diff --git a/tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py b/tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py
index 4b3ff25e908501aa49e9539373918b20c22331c2..9fd3f604a03a9f7e0865819c1db3ee636570f072 100644
--- a/tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py
+++ b/tools/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder_unittest.py
@@ -153,6 +153,7 @@ class LinuxFindTest(FindTestBase):
     self._files.append('../../../out/Debug/content_shell')
 
     self.has_google_chrome_on_path = False
+    self.chrome_beta_is_google_chrome = False
     this = self
     def call_hook(*args, **kwargs): # pylint: disable=W0613
       if this.has_google_chrome_on_path:
@@ -160,6 +161,12 @@ class LinuxFindTest(FindTestBase):
       raise OSError('Not found')
     self._finder_stubs.subprocess.call = call_hook
 
+    def realpath_hook(*unused_args, **unused_kwargs):
+      if this.chrome_beta_is_google_chrome:
+        return '/opt/google/chrome-beta/google-chrome-beta'
+      return '/opt/google/chrome/google-chrome'
+    self._finder_stubs.os.path.realpath = realpath_hook
+
   def testFindAllWithExact(self):
     if not self.CanFindAvailableBrowsers():
       return
@@ -194,12 +201,23 @@ class LinuxFindTest(FindTestBase):
     del self._files[1]
     self.has_google_chrome_on_path = True
     self.assertIn('system', self.DoFindAllTypes())
+    self.assertIn('stable', self.DoFindAllTypes())
+    self.assertIn('beta', self.DoFindAllTypes())
+    self.assertIn('dev', self.DoFindAllTypes())
 
     self.has_google_chrome_on_path = False
     del self._files[1]
     self.assertEquals(['content-shell-debug', 'content-shell-release'],
                       self.DoFindAllTypes())
 
+    self.has_google_chrome_on_path = True
+    self.chrome_beta_is_google_chrome = True
+
+    google_chrome = [browser for browser in self.DoFindAll()
+                     if browser._local_executable == 'google-chrome'][0]
+    self.assertEquals('/opt/google/chrome-beta',
+                      google_chrome._browser_directory)
+
   def testFindUsingRelease(self):
     if not self.CanFindAvailableBrowsers():
       return