Move ALL_BROWSER_TYPES constant to a FindAllBrowsers() function, so that it doesn't run unnecessari…

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

Index: tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py b/tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py
index 8424d979bcb53dc1a80a8418c853774fb6757ba4..3f1fbeeeaae82a000ef4b9291030efc63f687864 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/android_browser_finder.py
@@ -61,16 +61,15 @@ CHROME_PACKAGE_NAMES = {
        None]
 }
 
-ALL_BROWSER_TYPES = CHROME_PACKAGE_NAMES.keys()
-
 
 class PossibleAndroidBrowser(possible_browser.PossibleBrowser):
   """A launchable android browser instance."""
   def __init__(self, browser_type, finder_options, backend_settings, apk_name):
     super(PossibleAndroidBrowser, self).__init__(browser_type, 'android',
         finder_options, backend_settings.supports_tab_control)
-    assert browser_type in ALL_BROWSER_TYPES, \
-        'Please add %s to ALL_BROWSER_TYPES' % browser_type
+    assert browser_type in FindAllBrowserTypes(), \
+        ('Please add %s to android_browser_finder.FindAllBrowserTypes' %
+         browser_type)
     self._backend_settings = backend_settings
     self._local_apk = None
 
@@ -178,6 +177,10 @@ def CanFindAvailableBrowsers(logging=real_logging):
   return False
 
 
+def FindAllBrowserTypes():
+  return CHROME_PACKAGE_NAMES.keys()
+
+
 def FindAllAvailableBrowsers(finder_options, logging=real_logging):
   """Finds all the desktop browsers available on this machine."""
   if not CanFindAvailableBrowsers(logging=logging):