Ignore comments in histograms.xml leaf tags.

Change-Id: I4cd59c9a8e245ea3af4fcdb0bdd602f066c6fef0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610310Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Nik Bhagat <nikunjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662997}

tools/metrics/histograms/extract_histograms.py

@@ -79,7 +79,8 @@ class Error(Exception):
 def _JoinChildNodes(tag):
   """Join child nodes into a single text.
 
-  Applicable to leafs like 'summary' and 'detail'.
+  Applicable to leafs like 'summary' and 'detail'. Removes any comment in the
+  node.
 
   Args:
     tag: parent node
@@ -87,7 +88,9 @@ def _JoinChildNodes(tag):
   Returns:
     a string with concatenated nodes' text representation.
   """
-  return ''.join(c.toxml() for c in tag.childNodes).strip()
+  return ''.join(c.toxml()
+                 for c in tag.childNodes
+                 if c.nodeType != xml.dom.minidom.Node.COMMENT_NODE).strip()
 
 
 def _NormalizeString(s):

tools/metrics/histograms/extract_histograms_test.py

@@ -46,7 +46,11 @@ class ExtractHistogramsTest(unittest.TestCase):
  <histogram name="Test.Histogram" units="things">
   <owner> Please list the metric's owners. Add more owner tags as needed.
   </owner>
-  <summary> This is a summary </summary>
+  <summary>
+    <!-- Comments are fine -->
+    This is a summary
+    <!-- Comments are fine -->
+  </summary>
  </histogram>
 </histograms>
 </histogram-configuration>