[Android] Add context manager to record logcat during step(s).

scripts/slave/recipe_modules/chromium_android/example.expected/tester_no_devices.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "cleanup index.lock",
@@ skipping 436 matching lines @@
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "unittests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/tee.py",
-      "[SLAVE_BUILD]/src/out/Release/full_log",
+      "[SLAVE_BUILD]/src/out/Release/full_logcat",
       "--",
       "[SLAVE_BUILD]/src/build/android/adb_logcat_printer.py",
       "[SLAVE_BUILD]/src/out/logcat"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "logcat_dump"
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/src/third_party/android_platform/development/scripts/stack",
       "--arch",
       "arm",
       "--more-info",
-      "[SLAVE_BUILD]/src/out/Release/full_log"
+      "[SLAVE_BUILD]/src/out/Release/full_logcat"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "stack_tool_with_logcat_dump"
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/src/build/android/tombstones.py",
       "-a",
       "-s",
       "-w"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "stack_tool_for_tombstones"
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/src/build/android/asan_symbolize.py",
       "-l",
-      "[SLAVE_BUILD]/src/out/Release/full_log"
+      "[SLAVE_BUILD]/src/out/Release/full_logcat"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "stack_tool_for_asan"
   },
   {
     "name": "$result",
     "reason": "Infra Failure: Step('device_status_check') returned 1",
     "status_code": 1
   }
 ]