A couple fixes to find_unmapped_histograms.py.

tools/metrics/histograms/find_unmapped_histograms.py

Index: tools/metrics/histograms/find_unmapped_histograms.py
diff --git a/tools/metrics/histograms/find_unmapped_histograms.py b/tools/metrics/histograms/find_unmapped_histograms.py
index 443d1c6fa637413f68099e60d8f146bb65db4506..44d38bcf4484e680c6ba933b8bed7fc062eb371f 100644
--- a/tools/metrics/histograms/find_unmapped_histograms.py
+++ b/tools/metrics/histograms/find_unmapped_histograms.py
@@ -38,7 +38,7 @@ HISTOGRAM_REGEX = re.compile(r"""
     \w*            # Match the rest of the macro name, e.g. '_ENUMERATION'
     \(             # Match the opening parenthesis for the macro
     \s*            # Match any whitespace -- especially, any newlines
-    ([^,]*)        # Capture the first parameter to the macro
+    ([^,\)]*)      # Capture the first parameter to the macro

[Ilya Sherman, 2014/08/26 00:27:24]

Hmm, do you really need to escape the paren within a [] range?  Seems
surprising.

[Alexei Svitkine (slow), 2014/08/29 22:42:11]

You're right, it wasn't necessary. Done.

     ,              # Match the comma that delineates the first parameter

[Ilya Sherman, 2014/08/26 00:27:24]

Does this not need to be updated to allow for a paren as well?

[Alexei Svitkine (slow), 2014/08/29 22:42:11]

Done.

     """, re.VERBOSE)
 
@@ -113,10 +113,6 @@ def logNonLiteralHistogram(filename, histogram):
   if '\\' in histogram:
     return
 
-  # Field trials are unique within a session, so are effectively constants.
-  if histogram.startswith('base::FieldTrial::MakeName'):
-    return
-
   # Ignore histogram names that have been pulled out into C++ constants.
   if CONSTANT_REGEX.match(histogram):
     return