Clean up implementation of Dactyloscoper::RecordDirectSurface.

The clean-up is based on the comments left by japhet@ on

https://chromium-review.googlesource.com/c/chromium/src/+/2276401

Bug: None
Change-Id: Ifa6744a4299383bad5089589a93b1c99cb40ddc0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2284400Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Dylan Cutler <dylancutler@google.com>
Cr-Commit-Position: refs/heads/master@{#786053}

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

@@ -34,16 +34,13 @@ void Dactyloscoper::Record(ExecutionContext* context, WebFeature feature) {
 void Dactyloscoper::RecordDirectSurface(ExecutionContext* context,
                                         WebFeature feature,
                                         unsigned value) {
-  if (!context)
-    return;
   auto* window = DynamicTo<LocalDOMWindow>(context);
   if (!window)
     return;
-  if (Document* document = window->document()) {
-    IdentifiabilityMetricBuilder(document->UkmSourceID())
-        .SetWebfeature(feature, value)
-        .Record(document->UkmRecorder());
-  }
+  Document* document = window->document();
+  IdentifiabilityMetricBuilder(document->UkmSourceID())
+      .SetWebfeature(feature, value)
+      .Record(document->UkmRecorder());
 }
 
 void Dactyloscoper::RecordDirectSurface(ExecutionContext* context,