[Telemetry] Disable long running backgrounded gmail system health test on webview.

tools/perf/page_sets/system_health/long_running_stories.py

Index: tools/perf/page_sets/system_health/long_running_stories.py
diff --git a/tools/perf/page_sets/system_health/long_running_stories.py b/tools/perf/page_sets/system_health/long_running_stories.py
index 84fb53b4919cdca672d7c093f4a05cfc997003ab..2a70985470e68b495adb9a21a09f520106b3361c 100644
--- a/tools/perf/page_sets/system_health/long_running_stories.py
+++ b/tools/perf/page_sets/system_health/long_running_stories.py
@@ -6,6 +6,8 @@ from page_sets.login_helpers import google_login
 from page_sets.system_health import platforms
 from page_sets.system_health import system_health_story
 
+from telemetry import benchmark
+
 
 IDLE_TIME_IN_SECONDS = 100
 SAMPLING_INTERVAL_IN_SECONDS = 1
@@ -84,6 +86,7 @@ class LongRunningGmailDesktopForegroundStory(_LongRunningGmailDesktopBase):
   NAME = 'long_running:tools:gmail-foreground'
 
 
+@benchmark.Disabled('android-webview')  # Webview does not have tabs.
 class LongRunningGmailMobileBackgroundStory(_LongRunningGmailMobileBase):
   BACKGROUND = True
   NAME = 'long_running:tools:gmail-background'