[Telemetry] Allow telemetry to run without adb root.

tools/telemetry/telemetry/android_browser_backend.py

Index: tools/telemetry/telemetry/android_browser_backend.py
diff --git a/tools/telemetry/telemetry/android_browser_backend.py b/tools/telemetry/telemetry/android_browser_backend.py
index 04e8f1ceb291cb333c32408e59139e0851bb0a7d..07c26cac235e47f6f831c5b507d492cc004f176a 100644
--- a/tools/telemetry/telemetry/android_browser_backend.py
+++ b/tools/telemetry/telemetry/android_browser_backend.py
@@ -5,6 +5,7 @@ import json
 import logging
 import os
 import subprocess
+import sys
 import tempfile
 
 from telemetry import adb_commands
@@ -29,7 +30,7 @@ class AndroidBrowserBackend(browser_backend.BrowserBackend):
     self._devtools_remote_port = devtools_remote_port
 
     # Kill old browser.
-    self._adb.KillAll(self._package)
+    self._adb.CloseApplication(self._package)
     self._adb.KillAll('device_forwarder')
     self._adb.Forward('tcp:%d' % self._port, self._devtools_remote_port)
 
@@ -65,7 +66,7 @@ class AndroidBrowserBackend(browser_backend.BrowserBackend):
       self._adb.Push(f.name, cmdline_file)
 
     # Force devtools protocol on, if not already done.
-    if not is_content_shell:
+    if not is_content_shell and self._adb.IsRootEnabled():
       # Make sure we can find the apps' prefs file
       app_data_dir = '/data/data/%s' % self._package
       prefs_file = (app_data_dir +
@@ -110,6 +111,13 @@ class AndroidBrowserBackend(browser_backend.BrowserBackend):
     try:
       self._WaitForBrowserToComeUp()
       self._PostBrowserStartupInitialization()
+    except browser_gone_exception.BrowserGoneException:
+      logging.critical('Failed to connect to browser.')
+      if not self._adb.IsRootEnabled():
+        logging.critical(
+          'Ensure web debugging is enabled in Chrome at '
+          '"Settings > Developer tools > Enable USB Web debugging".')
+      sys.exit(1)
     except:
       import traceback
       traceback.print_exc()
@@ -128,7 +136,7 @@ class AndroidBrowserBackend(browser_backend.BrowserBackend):
     super(AndroidBrowserBackend, self).Close()
 
     self._adb.RunShellCommand('rm %s' % self._cmdline_file)
-    self._adb.KillAll(self._package)
+    self._adb.CloseApplication(self._package)
 
   def IsBrowserRunning(self):
     pids = self._adb.ExtractPid(self._package)