Move AOSP bots to Android 4.3

scripts/slave/recipes/android_webview_aosp.expected/trybot.json

 [
   {
     "cmd": [
       "python", 
       "-u", 
       "[DEPOT_TOOLS_ROOT]/gclient.py", 
       "config", 
       "--spec", 
       "cache_dir = None\ndeps_os = {}\nhooks = []\nsolutions = [{'custom_deps': {}, 'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'svn://svn-mirror.golo.chromium.org/blink/trunk'}, 'deps_file': '', 'managed': True, 'name': 'src', 'safesync_url': None, 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}]\ntarget_os = []\ntarget_os_only = False"
     ], 
@@ skipping 148 matching lines @@
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   }, 
   {
     "cmd": [
       "[DEPOT_TOOLS_ROOT]/repo", 
       "init", 
       "-u", 
       "https://android.googlesource.com/platform/manifest", 
       "-b", 
-      "jb-mr1.1-dev"
+      "android-4.3_r2.1"
     ], 
     "cwd": "[SLAVE_BUILD_ROOT]/android-src", 
     "name": "repo init"
   }, 
   {
     "cmd": [
       "[SLAVE_BUILD_ROOT]/src/android_webview/buildbot/generate_local_manifest.py", 
       "[SLAVE_BUILD_ROOT]/android-src", 
-      "external/chromium_org", 
-      "--ndk-revision", 
-      "5049b437591600fb0d262e4215cee4226e63c6ce"
+      "external/chromium_org"
     ], 
     "name": "generate local manifest"
   }, 
   {
     "cmd": [
       "[DEPOT_TOOLS_ROOT]/repo", 
       "sync", 
       "-j16", 
       "-d", 
       "-f"
@@ skipping 36 matching lines @@
       "--src-dir", 
       "[SLAVE_BUILD_ROOT]/android-src", 
       "--build-tool", 
       "make-android", 
       "--verbose"
     ], 
     "cwd": "[SLAVE_BUILD_ROOT]", 
     "name": "compile"
   }
 ]