Refactor histogram_macros.h. This improves documentation for the macros in the file, moves LOCAL_* …

base/metrics/histogram_base.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_METRICS_HISTOGRAM_BASE_H_
 #define BASE_METRICS_HISTOGRAM_BASE_H_
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
@@ skipping 74 matching lines @@
 
 class BASE_EXPORT HistogramBase {
  public:
   typedef int32_t Sample;                // Used for samples.
   typedef subtle::Atomic32 AtomicCount;  // Used to count samples.
   typedef int32_t Count;  // Used to manipulate counts in temporaries.
 
   static const Sample kSampleType_MAX;  // INT_MAX
 
   enum Flags {
-    kNoFlags = 0,
+    kNoFlags = 0x0,
 
     // Histogram should be UMA uploaded.
     kUmaTargetedHistogramFlag = 0x1,
 
     // Indicates that this is a stability histogram. This flag exists to specify
     // which histograms should be included in the initial stability log. Please
     // refer to |MetricsService::PrepareInitialStabilityLog|.
     kUmaStabilityHistogramFlag = kUmaTargetedHistogramFlag | 0x2,
 
     // Indicates that the histogram was pickled to be sent across an IPC
     // Channel. If we observe this flag on a histogram being aggregated into
     // after IPC, then we are running in a single process mode, and the
     // aggregation should not take place (as we would be aggregating back into
     // the source histogram!).
     kIPCSerializationSourceFlag = 0x10,
 
     // Indicates that a callback exists for when a new sample is recorded on
     // this histogram. We store this as a flag with the histogram since
     // histograms can be in performance critical code, and this allows us
     // to shortcut looking up the callback if it doesn't exist.
     kCallbackExists = 0x20,
 
     // Indicates that the histogram is held in "persistent" memory and may
     // be accessible between processes. This is only possible if such a
     // memory segment has been created/attached, used to create a Persistent-
     // MemoryAllocator, and that loaded into the Histogram module before this
     // histogram is created.
     kIsPersistent = 0x40,
 
+    // TODO(rkaplow): Look into this, but looks like this is unused and can

[Mark P, 2016/09/23 19:30:41]

Resolve before submitting.
(I see only 4 cases this flag is referred to.  You should be able to fix these
in this changelist or in an easy follow-up changelist.  The TODO should not end
up in the codebase.)

[rkaplow, 2016/09/26 20:16:09]

I think there's a bit of cleanup associated with this, so would rather do in a
subsequent CL. I don't mind removing the TODO if you'd like but I think it makes
sense to commit for now so it doesn't get forgotten (or, less easily)

[Mark P, 2016/09/26 23:06:47]

Okay.

+    // be removed.
     // Only for Histogram and its sub classes: fancy bucket-naming support.
     kHexRangePrintingFlag = 0x8000,
   };
 
   // Histogram data inconsistency types.
   enum Inconsistency : uint32_t {
     NO_INCONSISTENCIES = 0x0,
     RANGE_CHECKSUM_ERROR = 0x1,
     BUCKET_ORDER_ERROR = 0x2,
     COUNT_HIGH_ERROR = 0x4,
@@ skipping 135 matching lines @@
 
   const std::string histogram_name_;
   AtomicCount flags_;
 
   DISALLOW_COPY_AND_ASSIGN(HistogramBase);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_BASE_H_