Improve presubmit for histogram name typos

Currently, _CheckUmaHistogramChanges detects the cases like calling
  UMA_HISTOGRAM_BOOLEAN("NonexistingHistogram.Typo", true)
when "NonexistingHistogram.Typo" is not a histogram name defined in
histograms.xml.

However, it won't detect the case when the name is after a line break:
  UMA_HISTOGRAM_BOOLEAN(
      "NonexistingHistogram.VeeeeeeeryLoooooooongName.WithSubitems",
      true)

This will be often the case once the check gets extended to Java,
where the UMA_HISTOGRAM* macros are replaced with the
RecordHistogram.record*Histogram methods, which have longer names.

Bug: 821981
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I71d01f3b7012e8a8d6c4628d67a470c57005cd56
Reviewed-on: https://chromium-review.googlesource.com/978219
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545676}

PRESUBMIT.py

@@ -731,9 +731,10 @@ def _CheckUmaHistogramChanges(input_api, output_api):
   the reverse: changes in histograms.xml not matched in the code itself."""
   touched_histograms = []
   histograms_xml_modifications = []
-  # For now, the check only detects the case of the macro and histogram names
-  # being on a single line.
   single_line_re = input_api.re.compile(r'\bUMA_HISTOGRAM.*\("(.*?)"')
+  split_line_prefix_re = input_api.re.compile(r'\bUMA_HISTOGRAM.*\(')
+  split_line_suffix_re = input_api.re.compile(r'^\s*"([^"]*)"')
+  last_line_matched_prefix = False
   for f in input_api.AffectedFiles():
     # If histograms.xml itself is modified, keep the modified lines for later.
     if f.LocalPath().endswith(('histograms.xml')):
@@ -742,9 +743,17 @@ def _CheckUmaHistogramChanges(input_api, output_api):
     if not f.LocalPath().endswith(('cc', 'mm', 'cpp')):
       continue
     for line_num, line in f.ChangedContents():
+      if last_line_matched_prefix:
+        suffix_found = split_line_suffix_re.search(line)
+        if suffix_found :
+          touched_histograms.append([suffix_found.group(1), f, line_num])
+          last_line_matched_prefix = False
+          continue
       found = single_line_re.search(line)
       if found:
         touched_histograms.append([found.group(1), f, line_num])
+        continue
+      last_line_matched_prefix = split_line_prefix_re.search(line)
 
   # Search for the touched histogram names in the local modifications to
   # histograms.xml, and, if not found, on the base histograms.xml file.

PRESUBMIT_test.py

@@ -130,6 +130,21 @@ class UmaHistogramChangeMatchedOrNotTest(unittest.TestCase):
                                                    MockOutputApi())
     self.assertEqual(0, len(warnings))
 
+  def testMultiLine(self):
+    diff_cc = ['UMA_HISTOGRAM_BOOLEAN(', '    "Multi.Line", true)']
+    diff_cc2 = ['UMA_HISTOGRAM_BOOLEAN(', '    "Multi.Line"', '    , true)']
+    mock_input_api = MockInputApi()
+    mock_input_api.files = [
+      MockFile('some/path/foo.cc', diff_cc),
+      MockFile('some/path/foo2.cc', diff_cc2),
+    ]
+    warnings = PRESUBMIT._CheckUmaHistogramChanges(mock_input_api,
+                                                   MockOutputApi())
+    self.assertEqual(1, len(warnings))
+    self.assertEqual('warning', warnings[0].type)
+    self.assertTrue('foo.cc' in warnings[0].items[0])
+    self.assertTrue('foo2.cc' in warnings[0].items[1])
+
 class BadExtensionsTest(unittest.TestCase):
   def testBadRejFile(self):
     mock_input_api = MockInputApi()