Rip out existing distributed tracing mechanisms

The current approach is very invasive, and doesn't work very well. Two
good reasons to rip it out.

The plan is to move to straight OpenTracing, since OpenTelemtry isn't
available yet.

java/client/src/org/openqa/selenium/remote/tracing/BUILD.bazel

@@ -8,13 +8,10 @@ java_library(
     exports = [
         # Exposed by tracing APIs
         "//java/client/src/org/openqa/selenium/remote/http",
+        "//third_party/java/opentracing:opentracing-api",
     ],
     deps = [
         "//java/client/src/org/openqa/selenium/remote/http",
-        "//third_party/java/contrib:opentracing-tracerresolver",
-        "//third_party/java/guava",
         "//third_party/java/opentracing:opentracing-api",
-        "//third_party/java/opentracing:opentracing-noop",
-        "//third_party/java/opentracing:opentracing-util",
     ],
 )

java/client/src/org/openqa/selenium/remote/tracing/HttpTracing.java

@@ -17,50 +17,62 @@
 
 package org.openqa.selenium.remote.tracing;
 
-import com.google.common.base.Strings;
-
-import org.openqa.selenium.remote.http.HttpRequest;
-
+import io.opentracing.Span;
+import io.opentracing.SpanContext;
+import io.opentracing.Tracer;
+import io.opentracing.propagation.Format;
+import io.opentracing.propagation.TextMapAdapter;
 import io.opentracing.tag.Tags;
+import org.openqa.selenium.remote.http.HttpRequest;
 
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Objects;
-import java.util.TreeMap;
-import java.util.function.Function;
 
 public class HttpTracing {
 
   private HttpTracing() {
     // Utility classes
   }
 
-  public static final Function<HttpRequest, Map<String, String>> AS_MAP = req -> {
-    Map<String, String> builder = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
-    for (String name : req.getHeaderNames()) {
-      if (Strings.isNullOrEmpty(name)) {
-        continue;
-      }
-
-      String value = req.getHeader(name);
-      if (Strings.isNullOrEmpty(value)) {
-        continue;
-      }
-
-      builder.put(name, value);
-    }
-    return Collections.unmodifiableMap(builder);
-  };
+  public static SpanContext extract(Tracer tracer, HttpRequest request) {
+    return tracer.extract(Format.Builtin.HTTP_HEADERS, new HttpRequestAdapter(request));
+  }
 
-  public static void inject(Span span, HttpRequest request) {
+  public static void inject(Tracer tracer, Span span, HttpRequest request) {
     Objects.requireNonNull(request, "Request must be set.");
     if (span == null) {
       return;
     }
 
-    span.addTag(Tags.HTTP_METHOD.getKey(), request.getMethod().toString());
-    span.addTag(Tags.HTTP_URL.getKey(), request.getUri());
+    span.setTag(Tags.HTTP_METHOD.getKey(), request.getMethod().toString());
+    span.setTag(Tags.HTTP_URL.getKey(), request.getUri());
 
-    span.inject(request::setHeader);
+    tracer.inject(span.context(), Format.Builtin.HTTP_HEADERS, new HttpRequestAdapter(request));
+  }
+
+  private static class HttpRequestAdapter extends TextMapAdapter {
+
+    public HttpRequestAdapter(HttpRequest request) {
+      super(asMap(request));
+    }
+
+    private static Map<String, String> asMap(HttpRequest request) {
+      Map<String, String> entries = new LinkedHashMap<>();
+      request.getHeaderNames().forEach(name ->
+        request.getHeaders(name).forEach(value -> {
+          if (value != null) {
+            entries.put(name, value);
+          }
+        })
+      );
+      return Collections.unmodifiableMap(entries);
+    }
+
+    @Override
+    public void put(String key, String value) {
+      super.put(key, value);
+    }
   }
 }