Add shell::Tracer object and wire up to --trace-startup on Android

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 00995e8337ac8666a9f8b5306f37d7de51076412..14c421e4c8218ea8032db24a37e4a2e3cf1732b8 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -884,12 +884,12 @@ def _CheckSpamLogging(input_api, output_api):
   black_list = (_EXCLUDED_PATHS +
                 _TEST_CODE_EXCLUDED_PATHS +
                 input_api.DEFAULT_BLACK_LIST +
-                (r"^base[\\\/]logging\.h$",
-                 r"^base[\\\/]logging\.cc$",
-                 r"^shell[\\\/]native_application_loader\.cc$",
-                 r"^sandbox[\\\/]linux[\\\/].*",
-                 r"^tools[\\\/]",
-                 r"^ui[\\\/]aura[\\\/]bench[\\\/]bench_main\.cc$",))
+                (r"^base/logging\.h$",
+                 r"^base/logging\.cc$",
+                 r"^shell/application_manager/network_fetcher\.cc$",
+                 r"^shell/tracer\.cc$",
+                 r"^sandbox/linux/.*",
+                 r"^tools/"))
   source_file_filter = lambda x: input_api.FilterSourceFile(
       x, white_list=(file_inclusion_pattern,), black_list=black_list)
 
@@ -1025,20 +1025,9 @@ def _CheckUserActionUpdate(input_api, output_api):
   return []
 
 
-def _GetJSONParseError(input_api, filename, eat_comments=True):
+def _GetJSONParseError(input_api, filename):
   try:
     contents = input_api.ReadFile(filename)
-    if eat_comments:
-      json_comment_eater = input_api.os_path.join(
-          input_api.PresubmitLocalPath(),
-          'tools', 'json_comment_eater', 'json_comment_eater.py')
-      process = input_api.subprocess.Popen(
-          [input_api.python_executable, json_comment_eater],
-          stdin=input_api.subprocess.PIPE,
-          stdout=input_api.subprocess.PIPE,
-          universal_newlines=True)
-      (contents, _) = process.communicate(input=contents)
-
     input_api.json.loads(contents)
   except ValueError as e:
     return e