Revision Info into GenericSet

docs/how-to-write-metrics.md

 <!-- Copyright 2016 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.
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 # How to Write Metrics
 
 Timeline-Based Measurement v2 is a system for computing metrics from traces.
 
 A TBM2 metric is a Javascript function that takes a trace Model and produces
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  * [TelemetryInfo](/tracing/tracing/value/diagnostics/telemetry_info.html):
    This is automatically attached to every Histogram produced by telemetry.
    Structurally, it's a class with explicit named fields.
    Conceptually, it contains information about the origins of the trace that was
    consumed by the metric that produced the Histogram, such as the benchmark
    name, story name, benchmark start timestamp, etc.
    Visually, TelemetryInfos are displayed as a table.
 
    ![](/docs/images/how-to-write-metrics-telemetry.png)
 
- * [RevisionInfo](/tracing/tracing/value/diagnostics/revision_info.html):
-   This is automatically attached to every Histogram produced by telemetry.
-   Structurally, it's a class with explicit named fields. Conceptually, it
-   contains ranges of revisions of the software used to produce the trace that
-   was consumed by the metric that produced the Histogram, such as the Chromium
-   revision, v8 revision, and catapult revision. Visually, RevisionInfos are
-   displayed as a table.
-
-   ![](/docs/images/how-to-write-metrics-revision.png)
-
  * [BuildbotInfo](/tracing/tracing/value/diagnostics/buildbot_info.html):
    This is automatically attached to every Histogram produced by Chrome's
    performance testing buildbots. Structurally, it's a class with explicit named
    fields. Conceptually, it contains information about the buildbot process that
    ran telemetry. Visually, it is displayed as a table.
 
    ![](/docs/images/how-to-write-metrics-buildbot.png)
 
 ### Other Diagnostics
 
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   * Instead of having one category for all story grouping keys, each grouping
     individual grouping key may be listed as a category. For example, in Page
     Cycler v2 benchmarks, the "cache_temperature" grouping key would be
     displayed as a category.
 * Choosing groups builds a hierarchy of histograms that is filled in by merging
   histograms from the bottom up. Expanding the rows of histogram-set-table, any
   leaf nodes are histograms that were loaded, and their ancestors are computed by
   merging.
 * histogram-set-table uses the "label" property of TelemetryInfo to define the
   columns of the table.