Remove opencensus-impl dependency.

Author: HailongWen

google-cloud-bom/pom.xml

@@ -1047,11 +1047,6 @@
         <artifactId>opencensus-api</artifactId>
         <version>${opencensus.version}</version>
       </dependency>
-      <dependency>
-        <groupId>io.opencensus</groupId>
-        <artifactId>opencensus-impl</artifactId>
-        <version>${opencensus.version}</version>
-      </dependency>
       <dependency>
         <groupId>io.opencensus</groupId>
         <artifactId>opencensus-contrib-grpc-util</artifactId>

google-cloud-core-http/pom.xml

@@ -127,10 +127,6 @@
       <groupId>io.opencensus</groupId>
       <artifactId>opencensus-api</artifactId>
     </dependency>
-    <dependency>
-      <groupId>io.opencensus</groupId>
-      <artifactId>opencensus-impl</artifactId>
-    </dependency>
     <dependency>
       <groupId>io.opencensus</groupId>
       <artifactId>opencensus-contrib-http-util</artifactId>

google-cloud-core-http/src/test/java/com/google/cloud/http/CensusHttpModuleTest.java

@@ -19,6 +19,7 @@
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.easymock.EasyMock.createMock;
+import static org.easymock.EasyMock.createMockBuilder;
 import static org.easymock.EasyMock.replay;
 import static org.easymock.EasyMock.verify;
 
@@ -30,11 +31,18 @@
 import com.google.api.client.http.javanet.NetHttpTransport;
 
 import io.opencensus.common.Scope;
+import io.opencensus.trace.Span;
+import io.opencensus.trace.SpanContext;
+import io.opencensus.trace.SpanId;
+import io.opencensus.trace.TraceId;
+import io.opencensus.trace.TraceOptions;
 import io.opencensus.trace.Tracer;
 import io.opencensus.trace.Tracing;
 import io.opencensus.trace.propagation.TextFormat;
 
 import java.io.IOException;
+import java.util.EnumSet;
+import java.util.Random;
 
 import org.junit.Before;
 import org.junit.Rule;
@@ -105,7 +113,16 @@ public void censusHttpExecuteInterceptorShouldExecuteOriginal() throws IOExcepti
 
   @Test
   public void censusHttpExecuteInterceptorShouldInjectHeader() throws IOException {
-    Scope scope = censusHttpModule.getTracer().spanBuilder("Test span").startScopedSpan();
+    Random random = new Random();
+    SpanContext spanContext = SpanContext.create(
+        TraceId.generateRandomId(random),
+        SpanId.generateRandomId(random),
+        TraceOptions.DEFAULT);
+    Span mockSpan = createMockBuilder(Span.class)
+        .withConstructor(SpanContext.class, EnumSet.class)
+        .withArgs(spanContext, null)
+        .createMock();
+    Scope scope = tracer.withSpan(mockSpan);
     try {
       HttpExecuteInterceptor interceptor = censusHttpModule.new CensusHttpExecuteInterceptor(null);
       interceptor.intercept(httpRequest);