BASELINE: Update Chromium to 85.0.4183.14085-based

Change-Id: Iaa42f4680837c57725b1344f108c0196741f6057
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 68 insertions, 0 deletions

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+# Privacy Budget: Code Locations
+
+Following on from the high level [Privacy
+Budget](https://github.com/bslassey/privacy-budget) explainer, the current
+implementation focuses on measuring the identifiability of various web exposed
+features. Hence the word `Identifiability` occurs often in the code and
+documentation.
+
+This document focuses on code layout for Privacy Budget. Concepts and background
+for the identifiability study are out of scope.
+
+TODO(asanka): Link to study documents once they are checked in.
+
+## Core Metrics and Aggregation
+
+Locations:
+
+* [`third_party/blink/public/common/privacy_budget`](../third_party/blink/public/common/privacy_budget)
+* [`third_party/blink/common/privacy_budget`](../third_party/blink/common/privacy_budget)
+
+Includes:
+
+* Core logic and primitives for constructing identifiability metrics.
+
+  This is what one would use when reporting identifiability study samples.
+  Centralized logic makes it easier to construct consistent and stable samples.
+
+* Per-process aggregation of metrics.
+
+  Aggregation minimizes the amount of information being communicated across
+  process boundaries.
+
+The code in this directory is shared across `//content`, `//chrome`, and
+`//third_party/blink`. Hence its placement in `blink/public/common`.
+
+In addition, this directory also contains logic for per-process aggregation of
+metrics so that they can be efficiently communicated across process boundaries.
+
+## Static study settings
+
+Locations:
+
+* [`chrome/common/privacy_budget`](../chrome/common/privacy_budget)
+
+Logic for accessing per-session settings based on externally supplied field
+trial configurations. The full set of externally controlled settings are
+in
+[`privacy_budget_features.h`](../chrome/common/privacy_budget/privacy_budget_features.h).
+
+At a high level, these settings control such things as:
+
+* Whether the study is active.
+* Which identifiable surfaces should *not* be sampled.
+* Parameters for how surfaces are selected for sampling.
+
+Both the browser and the renderer need to access these settings. The browser
+needs them for filtering and reporting. The renderer needs them to avoid
+sampling surfaces where sampling itself is harmful for performance or stability
+reasons.
+
+## Persistent study state and reporting
+
+Locations:
+* [`chrome/browser/privacy_budget`](../chrome/browser/privacy_budget)
+
+Per-client state is primarily used and exposed by `IdentifiabilityStudyState`
+([Source](../chrome/browser/privacy_budget/identifiability_study_state.h)).
+