[DO NOT COMMIT] Refactor systrace to support new clock sync design

systrace/systrace/update_systrace_trace_viewer.py

Index: systrace/systrace/update_systrace_trace_viewer.py
diff --git a/systrace/systrace/update_systrace_trace_viewer.py b/systrace/systrace/update_systrace_trace_viewer.py
index 09eb0553298fbcdf337611c7e25c801a8d30d24a..46087b9ee8837a8d546a1298061061655a67fcf3 100755
--- a/systrace/systrace/update_systrace_trace_viewer.py
+++ b/systrace/systrace/update_systrace_trace_viewer.py
@@ -22,13 +22,23 @@ NO_AUTO_UPDATE_ = 'NO_AUTO_UPDATE'
 
 
 def create_catapult_rev_str_(revision):
+  """Create an HTML comment string giving the Catapult revision number.
+
+  Args:
+      revision: The revision number.
+  """
   return '<!--' + CATAPULT_REV_ + '=' + str(revision) + '-->'
 
 
-def get_catapult_rev_in_file_():
-  assert os.path.exists(SYSTRACE_TRACE_VIEWER_HTML_FILE_)
+def get_catapult_rev_in_file_(full_path):
+  """Determine the Catapult revision number of the existing trace viewer file.
+
+  Args:
+      full_path: Full path to the existing trace viewer file.
+  """
+  assert os.path.exists(full_path)
   rev = ''
-  with open(SYSTRACE_TRACE_VIEWER_HTML_FILE_, 'r') as f:
+  with open(full_path, 'r') as f:
     lines = f.readlines()
     for line in lines[::-1]:
       if CATAPULT_REV_ in line:
@@ -39,6 +49,10 @@ def get_catapult_rev_in_file_():
 
 
 def get_catapult_rev_in_git_():
+  """Determine the most recent Catapult revision number in git.
+
+  The Catapult revision number is the hash of the most recent commit.
+  """
   try:
     return subprocess.check_output(
         ['git', 'rev-parse', 'HEAD'],
@@ -47,7 +61,7 @@ def get_catapult_rev_in_git_():
     return ''
 
 
-def update(no_auto_update=False, no_min=False):
+def update(dest=None, no_auto_update=False, no_min=False):
   """Update the systrace trace viewer html file.
 
   When the html file exists, do not update the file if
@@ -55,11 +69,14 @@ def update(no_auto_update=False, no_min=False):
   2. or the revision is not changed.
 
   Args:
+    dest:           Directory to put the systrace_trace_viewer.html file.
     no_auto_update: If true, force updating the file with revision
                     NO_AUTO_UPDATE_. Future updates will be skipped unless this
                     argument is true again.
     no_min:         If true, skip minification when updating the file.
   """
+  output_html_file = os.path.join(dest, SYSTRACE_TRACE_VIEWER_HTML_FILE_)
+
   new_rev = None
   if no_auto_update:
     new_rev = NO_AUTO_UPDATE_
@@ -68,13 +85,12 @@ def update(no_auto_update=False, no_min=False):
     if not new_rev:
       return
 
-    if os.path.exists(SYSTRACE_TRACE_VIEWER_HTML_FILE_):
-      rev_in_file = get_catapult_rev_in_file_()
+    if os.path.exists(output_html_file):
+      rev_in_file = get_catapult_rev_in_file_(output_html_file)
       if rev_in_file == NO_AUTO_UPDATE_ or rev_in_file == new_rev:
         return
 
   # Generate the vulcanized result.
-  output_html_file = SYSTRACE_TRACE_VIEWER_HTML_FILE_
   with codecs.open(output_html_file, encoding='utf-8', mode='w') as f:
     vulcanize_trace_viewer.WriteTraceViewer(
         f,