Instrument NavigatorDeviceMemory to see if it leaks entropy about users' cross-origin identity.

We use IdentifiabilityMetricBuilder to report hashes of the different
values this method can return to UKM to determine how much entropy
this function leaks.

Bug: 973801
Change-Id: I4aa45f5662d62a83f1971a62c61891f3ebdfa81b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2186997
Commit-Queue: Dylan Cutler <dylancutler@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#769839}

third_party/blink/renderer/core/frame/navigator.cc

@@ -39,8 +39,9 @@
 namespace blink {
 
 Navigator::Navigator(LocalFrame* frame)
-    : NavigatorLanguage(frame ? frame->DomWindow() : nullptr),
-      ExecutionContextClient(frame) {}
+    : ExecutionContextClient(frame),
+      NavigatorDeviceMemory(frame ? frame->GetDocument() : nullptr),
+      NavigatorLanguage(frame ? frame->DomWindow() : nullptr) {}
 
 String Navigator::productSub() const {
   return "20030107";
@@ -119,6 +120,7 @@ void Navigator::Trace(Visitor* visitor) const {
   NavigatorLanguage::Trace(visitor);
   ExecutionContextClient::Trace(visitor);
   Supplementable<Navigator>::Trace(visitor);
+  NavigatorDeviceMemory::Trace(visitor);
 }
 
 ExecutionContext* Navigator::GetUAExecutionContext() const {

third_party/blink/renderer/core/frame/navigator.h

@@ -39,13 +39,13 @@ namespace blink {
 class LocalFrame;
 
 class CORE_EXPORT Navigator final : public ScriptWrappable,
+                                    public ExecutionContextClient,
                                     public NavigatorConcurrentHardware,
                                     public NavigatorDeviceMemory,
                                     public NavigatorID,
                                     public NavigatorLanguage,
                                     public NavigatorOnLine,
                                     public NavigatorUA,
-                                    public ExecutionContextClient,
                                     public Supplementable<Navigator> {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(Navigator);

third_party/blink/renderer/core/frame/navigator_device_memory.cc

@@ -5,11 +5,33 @@
 #include "third_party/blink/renderer/core/frame/navigator_device_memory.h"
 
 #include "third_party/blink/public/common/device_memory/approximated_device_memory.h"
+#include "third_party/blink/public/common/privacy_budget/identifiability_metrics.h"
+#include "third_party/blink/public/common/privacy_budget/identifiability_metric_builder.h"
+#include "third_party/blink/public/mojom/web_feature/web_feature.mojom-shared.h"
+#include "third_party/blink/renderer/core/dom/document.h"
+#include "third_party/blink/renderer/core/frame/local_dom_window.h"
 
 namespace blink {
 
+NavigatorDeviceMemory::NavigatorDeviceMemory(Document* document)
+    : document_(document) {}
+
 float NavigatorDeviceMemory::deviceMemory() const {
-  return ApproximatedDeviceMemory::GetApproximatedDeviceMemory();
+  float result = ApproximatedDeviceMemory::GetApproximatedDeviceMemory();
+  if (document_) {
+    IdentifiabilityMetricBuilder(
+        base::UkmSourceId::FromInt64(document_->UkmSourceID()))
+        .Set(IdentifiableSurface::FromTypeAndInput(
+                IdentifiableSurface::Type::kWebFeature,
+                static_cast<uint64_t>(WebFeature::kNavigatorDeviceMemory)),
+            IdentifiabilityDigestHelper(result))
+        .Record(document_->UkmRecorder());
+  }
+  return result;
+}
+
+void NavigatorDeviceMemory::Trace(Visitor* visitor) const {
+  visitor->Trace(document_);
 }
 
 }  // namespace blink

third_party/blink/renderer/core/frame/navigator_device_memory.h

@@ -6,12 +6,19 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_NAVIGATOR_DEVICE_MEMORY_H_
 
 #include "third_party/blink/renderer/core/core_export.h"
+#include "third_party/blink/renderer/core/dom/document.h"
 
 namespace blink {
 
-class CORE_EXPORT NavigatorDeviceMemory {
+class CORE_EXPORT NavigatorDeviceMemory : public GarbageCollectedMixin {
  public:
+  explicit NavigatorDeviceMemory();
+  explicit NavigatorDeviceMemory(Document* document);
   float deviceMemory() const;
+  void Trace(Visitor*) const override;
+
+ private:
+  WeakMember<Document> document_;
 };
 
 }  // namespace blink

third_party/blink/renderer/core/workers/worker_navigator.cc

@@ -40,6 +40,7 @@ WorkerNavigator::WorkerNavigator(const String& user_agent,
                                  const UserAgentMetadata& ua_metadata,
                                  ExecutionContext* execution_context)
     : ExecutionContextClient(execution_context),
+      NavigatorDeviceMemory(nullptr),
       NavigatorLanguage(execution_context),
       user_agent_(user_agent),
       ua_metadata_(ua_metadata) {}
@@ -73,6 +74,7 @@ void WorkerNavigator::Trace(Visitor* visitor) const {
   ExecutionContextClient::Trace(visitor);
   NavigatorLanguage::Trace(visitor);
   Supplementable<WorkerNavigator>::Trace(visitor);
+  NavigatorDeviceMemory::Trace(visitor);
 }
 
 }  // namespace blink