Support a shorthand to set<variant>'s summary attribute

Support a shorthand to use the variant's name to format the generated
histogram's summary when the variant's summary attribute is omitted.

Bug: 758782
Change-Id: I38d8659be97cdc26d3f0e0eb692bf423aded82b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2387205
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Auto-Submit: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803627}

tools/metrics/histograms/extract_histograms.py

@@ -488,16 +488,18 @@ def _ExtractVariantNodes(node):
   """
   variant_list = []
   for variant_node in IterElementsWithTag(node, 'variant', 1):
-    variant = dict(name=variant_node.getAttribute('name'),
-                   summary=variant_node.getAttribute('summary'))
+    name = variant_node.getAttribute('name')
+    summary = variant_node.getAttribute('summary') if variant_node.hasAttribute(
+        'summary') else name
+    variant = dict(name=name, summary=summary)
 
     obsolete_text = _GetObsoleteReason(variant_node)
     if obsolete_text:
       variant['obsolete'] = obsolete_text
 
-    variant_owners, variant_has_owners = _ExtractOwners(variant_node)
+    owners, variant_has_owners = _ExtractOwners(variant_node)
     if variant_has_owners:
-      variant['owners'] = variant_owners
+      variant['owners'] = owners
 
     variant_list.append(variant)
 

tools/metrics/histograms/extract_histograms_test.py

@@ -121,18 +121,18 @@ TEST_BASE_HISTOGRAM_XML_CONTENT = """
 TEST_HISTOGRAM_WITH_TOKENS = """
 <histogram-configuration>
 <histograms>
-<histogram name="HistogramName{Color}{Size}" expires_after="2017-10-16">
+<histogram name="HistogramName.{Color}{Size}" expires_after="2017-10-16">
   <owner>me@chromium.org</owner>
   <summary>
     This is a histogram for button of {Color} color and {Size} size.
   </summary>
   <token key="Color">
-    <variant name=".red" summary="red">
+    <variant name="red">
       <obsolete>
         Obsolete red
       </obsolete>
     </variant>
-    <variant name=".green" summary="green">
+    <variant name="green">
       <owner>green@chromium.org</owner>
     </variant>
   </token>
@@ -167,18 +167,18 @@ TEST_HISTOGRAM_WITH_VARIANTS = """
   <variant name=".large" summary="large"/>
 </variants>
 
-<histogram name="HistogramName{Color}{Size}" expires_after="2017-10-16">
+<histogram name="HistogramName.{Color}{Size}" expires_after="2017-10-16">
   <owner>me@chromium.org</owner>
   <summary>
     This is a histogram for button of {Color} color and {Size} size.
   </summary>
   <token key="Color">
-    <variant name=".red" summary="red">
+    <variant name="red">
       <obsolete>
         Obsolete red
       </obsolete>
     </variant>
-    <variant name=".green" summary="green">
+    <variant name="green">
       <owner>green@chromium.org</owner>
     </variant>
   </token>
@@ -690,6 +690,8 @@ class ExtractHistogramsTest(unittest.TestCase):
         histogram_with_token, {})
     histograms_dict, _ = extract_histograms._UpdateHistogramsWithTokens(
         histograms_dict)
+    # Use the variant's name to format the summary when the variant's summary
+    # attribute is omitted.
     self.assertEqual(
         'This is a histogram for button of red color and small size.',
         histograms_dict['HistogramName.red.small']['summary'])