Add UKM collection for HTMLCanvas readbacks and RenderingContext creations.

Bug: 973801
Change-Id: Ifa3c3e2a26187b0b813a5984e7ad75b97f9ba53c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2173394
Commit-Queue: Chris Fredrickson <cfredric@google.com>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#766557}

third_party/blink/public/common/privacy_budget/identifiable_surface.h

@@ -42,6 +42,10 @@ class IdentifiableSurface {
     // Input is a mojom::WebFeature
     kWebFeature = 1,
 
+    // Represents a readback of a canvas. Input is the
+    // CanvasRenderingContextType.
+    kCanvasReadback = 2,
+
     // We can use values up to and including |kMax|.
     kMax = 0xff
   };

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2618,6 +2618,7 @@ enum WebFeature {
   kV8HTMLVideoElement_CancelVideoFrameCallback_Method = 3281,
   kRubyElementWithDisplayBlock = 3282,
   kLocationFragmentDirectiveAccessed = 3283,
+  kCanvasRenderingContext = 3284,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/core/html/canvas/canvas_rendering_context_host.h

@@ -79,6 +79,12 @@ class CORE_EXPORT CanvasRenderingContextHost : public CanvasResourceHost,
   virtual void Commit(scoped_refptr<CanvasResource> canvas_resource,
                       const SkIRect& damage_rect);
 
+  // For deferred canvases this will have the side effect of drawing recorded
+  // commands in order to finalize the frame.
+  virtual ScriptPromise convertToBlob(ScriptState*,
+                                      const ImageEncodeOptions*,
+                                      ExceptionState&);
+
   bool IsPaintable() const;
 
   // Required by template functions in WebGLRenderingContextBase
@@ -96,12 +102,6 @@ class CORE_EXPORT CanvasRenderingContextHost : public CanvasResourceHost,
   bool Is2d() const;
   CanvasColorParams ColorParams() const;
 
-  // For deferred canvases this will have the side effect of drawing recorded
-  // commands in order to finalize the frame.
-  ScriptPromise convertToBlob(ScriptState*,
-                              const ImageEncodeOptions*,
-                              ExceptionState&);
-
   // blink::CanvasImageSource
   bool IsOffscreenCanvas() const override;
 

third_party/blink/renderer/core/html/canvas/html_canvas_element.cc

@@ -38,7 +38,10 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/numerics/checked_math.h"
 #include "build/build_config.h"
+#include "services/metrics/public/cpp/ukm_recorder.h"
 #include "third_party/blink/public/common/features.h"
+#include "third_party/blink/public/common/privacy_budget/identifiability_metric_builder.h"
+#include "third_party/blink/public/common/privacy_budget/identifiability_metrics.h"
 #include "third_party/blink/public/platform/task_type.h"
 #include "third_party/blink/public/resources/grit/blink_image_resources.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_controller.h"
@@ -55,6 +58,7 @@
 #include "third_party/blink/renderer/core/frame/local_frame.h"
 #include "third_party/blink/renderer/core/frame/local_frame_client.h"
 #include "third_party/blink/renderer/core/frame/settings.h"
+#include "third_party/blink/renderer/core/frame/web_feature.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_async_blob_creator.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_context_creation_attributes_core.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_draw_listener.h"
@@ -249,6 +253,15 @@ void HTMLCanvasElement::RegisterRenderingContextFactory(
   RenderingContextFactories()[type] = std::move(rendering_context_factory);
 }
 
+void HTMLCanvasElement::RecordIdentifiabilityMetric(
+    const blink::IdentifiableSurface& surface,
+    int64_t value) const {
+  blink::IdentifiabilityMetricBuilder(
+      base::UkmSourceId::FromInt64(GetDocument().UkmSourceID()))
+      .Set(surface, value)
+      .Record(GetDocument().UkmRecorder());
+}
+
 CanvasRenderingContext* HTMLCanvasElement::GetCanvasRenderingContext(
     const String& type,
     const CanvasContextCreationAttributesCore& attributes) {
@@ -271,8 +284,14 @@ CanvasRenderingContext* HTMLCanvasElement::GetCanvasRenderingContextInternal(
   }
 
   // Log the aliased context type used.
-  if (!context_)
+  if (!context_) {
+    RecordIdentifiabilityMetric(
+        blink::IdentifiableSurface::FromTypeAndInput(
+            blink::IdentifiableSurface::Type::kWebFeature,
+            static_cast<uint64_t>(blink::WebFeature::kCanvasRenderingContext)),
+        blink::IdentifiabilityDigestHelper(context_type));
     UMA_HISTOGRAM_ENUMERATION("Blink.Canvas.ContextType", context_type);
+  }
 
   context_type =
       CanvasRenderingContext::ResolveContextTypeAliases(context_type);
@@ -354,6 +373,20 @@ CanvasRenderingContext* HTMLCanvasElement::GetCanvasRenderingContextInternal(
   return context_.Get();
 }
 
+ScriptPromise HTMLCanvasElement::convertToBlob(
+    ScriptState* script_state,
+    const ImageEncodeOptions* options,
+    ExceptionState& exception_state) {
+  RecordIdentifiabilityMetric(
+      blink::IdentifiableSurface::FromTypeAndInput(
+          blink::IdentifiableSurface::Type::kCanvasReadback,
+          context_ ? context_->GetContextType()
+                   : CanvasRenderingContext::kContextTypeUnknown),
+      0);
+  return CanvasRenderingContextHost::convertToBlob(script_state, options,
+                                                   exception_state);
+}
+
 bool HTMLCanvasElement::ShouldBeDirectComposited() const {
   return (context_ && context_->IsComposited()) || (!!surface_layer_bridge_);
 }
@@ -925,6 +958,12 @@ String HTMLCanvasElement::ToDataURLInternal(
       // Currently we only support three encoding types.
       NOTREACHED();
     }
+    RecordIdentifiabilityMetric(
+        blink::IdentifiableSurface::FromTypeAndInput(
+            blink::IdentifiableSurface::Type::kCanvasReadback,
+            context_ ? context_->GetContextType()
+                     : CanvasRenderingContext::kContextTypeUnknown),
+        0);
     return data_url;
   }
 
@@ -991,6 +1030,13 @@ void HTMLCanvasElement::toBlob(V8BlobCallback* callback,
         GetExecutionContext());
   }
 
+  RecordIdentifiabilityMetric(
+      blink::IdentifiableSurface::FromTypeAndInput(
+          blink::IdentifiableSurface::Type::kCanvasReadback,
+          context_ ? context_->GetContextType()
+                   : CanvasRenderingContext::kContextTypeUnknown),
+      0);
+
   if (async_creator) {
     async_creator->ScheduleAsyncBlobCreation(quality);
   } else {

third_party/blink/renderer/core/html/canvas/html_canvas_element.h

@@ -32,6 +32,7 @@
 
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
+#include "third_party/blink/public/common/privacy_budget/identifiable_surface.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_value.h"
 #include "third_party/blink/renderer/bindings/core/v8/v8_blob_callback.h"
 #include "third_party/blink/renderer/core/core_export.h"
@@ -289,6 +290,10 @@ class CORE_EXPORT HTMLCanvasElement final
     context_creation_was_blocked_ = true;
   }
 
+  ScriptPromise convertToBlob(ScriptState*,
+                              const ImageEncodeOptions*,
+                              ExceptionState&) override;
+
   bool NeedsUnbufferedInputEvents() const { return needs_unbuffered_input_; }
 
   void SetNeedsUnbufferedInputEvents(bool value) {
@@ -314,6 +319,9 @@ class CORE_EXPORT HTMLCanvasElement final
  private:
   void Dispose();
 
+  void RecordIdentifiabilityMetric(const blink::IdentifiableSurface& surface,
+                                   int64_t value) const;
+
   void PaintInternal(GraphicsContext&, const PhysicalRect&);
 
   using ContextFactoryVector =

tools/metrics/histograms/enums.xml

@@ -27198,6 +27198,7 @@ Called by update_use_counter_feature_enum.py.-->
   <int value="3281" label="V8HTMLVideoElement_CancelVideoFrameCallback_Method"/>
   <int value="3282" label="RubyElementWithDisplayBlock"/>
   <int value="3283" label="LocationFragmentDirectiveAccessed"/>
+  <int value="3284" label="CanvasRenderingContext"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">