Clean up histograms.xml formatting

tools/metrics/histograms/print_style.py

Index: tools/metrics/histograms/print_style.py
diff --git a/tools/metrics/histograms/print_style.py b/tools/metrics/histograms/print_style.py
index 6b7064990c6141bb812ef69f4b3361a0c8ac26ca..21806657f2e9b77859b4a6a2eff39c92ede6c488 100644
--- a/tools/metrics/histograms/print_style.py
+++ b/tools/metrics/histograms/print_style.py
@@ -17,12 +17,12 @@ import pretty_print_xml
 ATTRIBUTE_ORDER = {
     'affected-histogram': ['name'],
     'details': [],
-    'enum': ['name', 'type'],
+    'enum': ['name'],
     'enums': [],
     'histogram': ['base', 'name', 'enum', 'units'],
     'histogram-configuration': ['logsource'],
-    'histogram_suffixes': ['name', 'separator', 'ordering'],
-    'histogram_suffixes_list': [],
+    'histogram-suffixes': ['name', 'separator', 'ordering'],
+    'histogram-suffixes-list': [],
     'histograms': [],
     'int': ['value', 'label'],
     'obsolete': [],
@@ -32,11 +32,20 @@ ATTRIBUTE_ORDER = {
     'with-suffix': ['name'],
 }
 
+# Attribute names that must be explicitly specified on nodes that support them.
+REQUIRED_ATTRIBUTES = [
+    # TODO(isherman): Make the 'label' attribute required as well. This requires
+    # fixing up existing suffixes that omit a label.
+    'name',
+    'separator',
+    'value',
+]
+
 # Tag names for top-level nodes whose children we don't want to indent.
 TAGS_THAT_DONT_INDENT = [
     'histogram-configuration',
     'histograms',
-    'histogram_suffixes_list',
+    'histogram-suffixes-list',
     'enums',
 ]
 
@@ -45,8 +54,8 @@ TAGS_THAT_DONT_INDENT = [
 TAGS_THAT_HAVE_EXTRA_NEWLINE = {
     'histogram-configuration': (2, 1, 1),
     'histograms': (2, 1, 1),
-    'histogram_suffixes_list': (2, 1, 1),
-    'histogram_suffixes': (1, 1, 1),
+    'histogram-suffixes-list': (2, 1, 1),
+    'histogram-suffixes': (1, 1, 1),
     'enums': (2, 1, 1),
     'histogram': (1, 1, 1),
     'enum': (1, 1, 1),
@@ -64,14 +73,15 @@ TAGS_ALPHABETIZATION_RULES = {
     'histograms': ('histogram', LOWERCASE_NAME_FN),
     'enums': ('enum', LOWERCASE_NAME_FN),
     'enum': ('int', lambda n: int(n.attributes['value'].value)),
-    'histogram_suffixes_list': ('histogram_suffixes', LOWERCASE_NAME_FN),
-    'histogram_suffixes': ('affected-histogram', LOWERCASE_NAME_FN),
+    'histogram-suffixes-list': ('histogram-suffixes', LOWERCASE_NAME_FN),
+    'histogram-suffixes': ('affected-histogram', LOWERCASE_NAME_FN),
 }
 
 
 def GetPrintStyle():
   """Returns an XmlStyle object for pretty printing histograms."""
   return pretty_print_xml.XmlStyle(ATTRIBUTE_ORDER,
+                                   REQUIRED_ATTRIBUTES,
                                    TAGS_THAT_HAVE_EXTRA_NEWLINE,
                                    TAGS_THAT_DONT_INDENT,
                                    TAGS_THAT_ALLOW_SINGLE_LINE,