[Telemetry] Disable session_restore.{cold,warm}.startup_pages on 10.6

These tests are flaky on OSX 10.6.
Also revert attempted fix: https://codereview.chromium.org/568673004 .

BUG=405386

Review URL: https://codereview.chromium.org/582803005

Cr-Commit-Position: refs/heads/master@{#295907}

tools/perf/benchmarks/session_restore.py

@@ -48,7 +48,8 @@ class SessionRestoreWarmTypical25(_SessionRestoreTest):
              'pageset_repeat': 20}
 
 
-@benchmark.Disabled('android', 'linux')  # crbug.com/325479, crbug.com/381990
+# crbug.com/325479, crbug.com/381990, crbug.com/405386
+@benchmark.Disabled('android', 'linux', 'snowleopard')
 class SessionRestoreWithUrlCold(_SessionRestoreTest):
   """Measure Chrome cold session restore with startup URLs."""
   tag = 'cold'
@@ -58,7 +59,8 @@ class SessionRestoreWithUrlCold(_SessionRestoreTest):
              'pageset_repeat': 5}
 
 
-@benchmark.Disabled('android', 'linux')  # crbug.com/325479, crbug.com/381990
+# crbug.com/325479, crbug.com/381990, crbug.com/405386
+@benchmark.Disabled('android', 'linux', 'snowleopard')
 class SessionRestoreWithUrlWarm(_SessionRestoreTest):
   """Measure Chrome warm session restore with startup URLs."""
   tag = 'warm'

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

@@ -144,7 +144,7 @@ class ChromeBrowserBackend(browser_backend.BrowserBackend):
 
   def _WaitForBrowserToComeUp(self, wait_for_extensions=True):
     try:
-      util.WaitFor(self.HasBrowserFinishedLaunching, timeout=50)
+      util.WaitFor(self.HasBrowserFinishedLaunching, timeout=30)
     except (util.TimeoutException, exceptions.ProcessGoneException) as e:
       if not self.IsBrowserRunning():
         raise exceptions.BrowserGoneException(self.browser, e)