Bring back error_prone_annotations

Author: suztomo

sdk-platform-java/api-common-java/pom.xml

@@ -60,6 +60,12 @@
             <artifactId>javax.annotation-api</artifactId>
             <version>${javax.annotation-api.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_annotations</artifactId>
+            <version>${errorprone.version}</version>
+            <scope>compile</scope>
+        </dependency>
         <!-- Test Dependencies -->
         <dependency>
             <groupId>junit</groupId>
@@ -117,6 +123,16 @@
                     </archive>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <configuration>
+                <ignoredUnusedDeclaredDependencies>
+                    <ignoredUnusedDeclaredDependency>com.google.errorprone:error_prone_annotations</ignoredUnusedDeclaredDependency>
+                </ignoredUnusedDeclaredDependencies>
+                </configuration>
+        </plugin>
+
         </plugins>
     </build>
 </project>

sdk-platform-java/gax-java/gax/pom.xml

@@ -41,13 +41,6 @@
     <dependency>
       <groupId> com.google.protobuf</groupId>
       <artifactId>protobuf-java-util</artifactId>
-      <exclusions>
-        <exclusion>
-          <!-- protobuf-java-util's error_prone_annotatoins is old. -->
-          <groupId>com.google.errorprone</groupId>
-          <artifactId>error_prone_annotations</artifactId>
-        </exclusion>
-      </exclusions>
     </dependency>
     <dependency>
       <groupId>org.threeten</groupId>